Two recent examples from Social Media:

Joe Bastardi: "Classic horribly biased reporting, BBC puts this out, but refuses to acknowledge that the planet is greener than ever in the satellite era. guess pictures of the greening earth won't lead to deception I dare the BBC to put that latter picture up, the reality of what is going on"

Tom Nelson: "'Forward projections of solar cyclicity imply the next few decades may be marked by global cooling rather than warming, despite continuing CO2 emissions' #NIPCC"

Reality is different. The denial that is underway has nothing to do with science. It is a rejection of science and the scientific method. A recent paper published in Nature Human Behavior distinguishes between scientific skepticism and the "science denialism" being advanced to mislead the public about climate change.

Science denialism must not be confused with scepticism. Scepticism towards scientific propositions is a crucial element of science itself. In fact, it functions as a driving force of scientific debates and increases the quality of new propositions via mechanisms such as peer review and the replication of experimental research. The common ground of this functional scepticism is the scientific ethos that scientists use data to update their prior beliefs regardless of the outcome. However, in contrast to functional scepticism, science deniers accept evidence only if it confirms their prior beliefs--that usually contradict the scientific consensus. This dysfunctional scepticism is driven by how the denier would like things to be rather than what he has evidence for, making science denialism a motivated rejection of science.

https://t.co/jysNBwsVA2

Bastardi's point ignores a key point about the "greening" that is underway: Arctic warming is leading to plant growth in a region that previously was too cold to support it. In other words, this plant growth provides confirmation of the climate change that Bastardi rejects.

For more than 35 years, satellites circling the Arctic have detected a “greening” trend in Earth’s northernmost landscapes. Scientists have attributed this verdant flush to more vigorous plant growth and a longer growing season, propelled by higher temperatures that come with climate change. But recently, satellites have been picking up a decline in tundra greenness in some parts of the Arctic. Those areas appear to be “browning.”

Like the salmonberry harvesters on the Kenai Peninsula, ecologists working on the ground have witnessed browning up close at field sites across the circumpolar Arctic, from Alaska to Greenland to northern Norway and Sweden. Yet the bushes bereft of berries and the tinder-dry heaths (low-growing shrubland) haven’t always been picked up by the satellites. The low-resolution sensors may have averaged out the mix of dead and living vegetation and failed to detect the browning.

https://phys.org/news/2018-08-ecosystems-greener-arctic.html

Nelson has cited solar activity to advance calls for global cooling to get underway. Yet, global temperatures continue to rise with little credible evidence of a decline and profound evidence of a decoupling from solar activity.

http://www.columbia.edu/~mhs119/Temperature/1880-1920base.png

The global temperature trend has diverged from solar irradiance. NASA observed:

One of the “smoking guns” that tells us the Sun is not causing global warming comes from looking at the amount of the Sun’s energy that hits the top of the atmosphere. Since 1978, scientists have been tracking this using sensors on satellites and what they tell us is that there has been no upward trend in the amount of the Sun’s energy reaching Earth.

A second smoking gun is that if the Sun were responsible for global warming, we would expect to see warming throughout all layers of the atmosphere, from the surface all the way up to the upper atmosphere (stratosphere). But what we actually see is warming at the surface and cooling in the stratosphere. This is consistent with the warming being caused by a build-up of heat-trapping gases near the surface of the Earth, and not by the Sun getting “hotter.”

https://climate.nasa.gov/faq/14/is-the-sun-causing-global-warming/

It is imperative that the public be able to sort fact from fiction. The body of literature on climate change is large and growing.

When it comes to the noisy movement to deny climate change, a good starting point is to ask why those who deny it have refused to put their ideas to peer review. It is easy to fire empty cannons from the sidelines. Peer review requires that one's ideas hold up to rigorous scrutiny that is a defining attribute of science. But, as noted above, science denialism is a rejection of science. Thus, the peer review channel is avoided.

So far ( date provided by Copernicus) :

January 2026 was the fifth-warmest January globally. 

February 2025 was the fifth-warmest Februar globally. 

Notables so far were the variations in temperature across N/A and parts of Europe.  These regions hosted the lion's share of what negative anomaly contribution there was that went into the total state of the planetary system. 

The graphic below illustrates these idiosyncrasies.

( I corroborated the above with NASA's releases and they conform )

March is not yet available at either Copernicus or NASA's monthly releases. NASA typically releases their finding s around the 10th of each month so we expect those soon. 

We know already that March 2026 was the warmest March on record across N/A mid latitude ( conterminous US), per more sources than need to really list here.  Go take a look.   However, again, both in data, as well as "sensibly" experienced, this was not as readily observed for the eastern mid latitude continent.  Nevertheless, these eastern geographies accumulated +2 to +3 positive anomaly for the month - so ours was likely still negative relative to the whole continent, which can be ratified soon enough.  This may or may not be reflected in the total graphics including the Mid Atlantic and eastern Ohio Valley and some parts of the SE.  

Personally, given a-priori awareness of the global circulation modes for the past 7 months and the persistence thereof, .. I suspect we'll see a repeat of relative offsets over eastern N/A and N-W Europe, while the rest of the world observes a ranking somewhere in the 3rd to 6th place for March.   

The beat goes on...

January 2025   ~ +1.8C above the pre 1850 level,  according to Copernicus

February 2025  ~ +1.8C above the pre 1850 level, according to Copernicus

March 2025 continued the remarkable trend, being the 2nd warmest March in the history of record,   https://phys.org/news/2025-04-global-temperatures-historic-highs-eu.html    

Powered by the warmest December and February on record, Phoenix experienced its warmest winter on record, by far. Its winter mean temperature of 63.9° was similar to a typical winter in Melbourne, FL. Its seasonal mean temperature also exceeded the figure from March-May 1917.

Table 6: Winter and Spring Mean Temperatures:

Table 12: Largest Difference between 1st and 2nd Warmest 3-Month Periods:

Updates:

World Weather Attribution's Flash Analysis of Western North America's March Heatwave

Phoenix Experiences Mind-Boggling March Warmth

March 2026 vs. April Comparisons

In the meantime,

Both extent and area are currently 4th lowest. Though area is threatening to fall to the 6th over the next few days if the losses remain mundane.

When looking strictly at Cat 5's - they  definitely seem to be getting more frequent over time, but also seem to correlate heavily with the solar cycles; specifically being more frequent during peaks of solar cycles, with perhaps some lag (more frequent on the "back side").

Here's list of Cat 5's by year:

https://en.wikipedia.org/wiki/List_of_Category_5_Atlantic_hurricanes

Haven't charted yet, but there definitely seems to be strong correlation with the peak and/or back side of the peak of solar cycles; specifically cat 5 frequency peaking:

https://en.wikipedia.org/wiki/Solar_cycle

Haven't charted the correlation (maybe someone else has) but it definitely seems to be there; looking at the list of Cat 5's at least.   The correlation seems to be strongest in recent years:

1924
1928  - solar cycle 16 peak
1932  - solar cycle 16 backside
1932
1933
1933
1935
1938  - solar cycle 17 peak backside
1944  - off-cycle
1953  - off-cycle
1955
1961  - solar cycle 19 peak backside
1961
1966
1967
1969  - solar cycle 20 peak
1971
1977
1979  - solar cycle 21 peak
1980
1988
1989  - solar cycle 22 peak
1992
1998
2003  - solar cycle 23 peak backside
2004
2005
2005
2005
2005
2007
2007
2016  - solar cycle 24 peak backside
2017
2017
2018
2019
2022
2024
2024
2025  - solar cycle 25 peak
2025
2025
 

Odd thing is that a google search mentions *anti-correlation* of hurricane activity and solar cycles - but that's not what I see here, at least looking at the Cat 5's.   Perhaps during peak periods there are less overall hurricanes, but more Cat 5's (?).

Driven by anthropogenic greenhouse gas emissions, there is an energy imbalance in the Earth’s climate system. More than 90% of the excess heat accumulated in the climate system is deposited in the world’s oceans. The ocean heat content (OHC) influences ocean–atmosphere interactions by providing thermal inertia to sea surface temperatures and thus exerts considerable control over the world’s weather. Rising ocean temperatures bolster the energy exchanges from ocean to atmosphere, increase the quantity of atmospheric moisture, and change the patterns of precipitation and temperature globally...

[G]lobal OHC has increased steadily, regardless of the status of ENSO, owing to anthropogenic influences. When considered on an annual basis, 2022 is the hottest year ever recorded in the world’s oceans. Its OHC exceeds that of 2021 by 10.9 ± 8.3 ZJ according to IAP/CAS data, and by 9.1 ± 8.7 ZJ according to NCEI/NOAA data (for the 0–2000 m water depth)...

The complete paper can be found here.

the stratosphere which we know GHGs like CO2 lead to cooling.  I found PEER reviewed papers on this that there indeed is a negative greenhouse effect on the Antarctic plateau. 

This was in Nature    https://www.nature.com/articles/s41612-018-0031-y   

So based on this, what happened during the last glacial maximum?  Much of the land masses in the NH were covered by similar ice sheets and likely had a negative greenhouse effect. Hence the argument that warming from orbital parameters warmed the planet and increased CO2 which then increased temperatures will not work over the ice sheets!   this argument always didn't sit well with me. If CO2 is the control knob for the climate, then why does it not kick off the climate changes?   If it is a feedback, it would cool the ice sheets! This paper also shows that the greenhouse effect is weakest in the polar regions (negative over Antarctic Plateau) and is strongest over the tropics which makes sense since water vapor IS the primary greenhouse gas.  CO2 is a weak GHG that somehow becomes stronger during times when ice sheets melt supposedly.  What changes in the quantam mechanics???  Anyway, I think this study changes how we see CO2 and its role in glacial and interglacial cycles. Water vapor is the primary GHG. That's my scientific opinion. 

 ...I'm interesting in establishing an ongoing discussion, ranging from disciplined research to general aspects involving environment.  It could/would encompass the total manifold that exists under the general rubric of "anthropomorphic pollution" . 

This is a weather -based social media platform, so it may not be entirely appropriate in the strictest sense ...  However, merely starting the thread in Off-Topic lounge probably doesn't get noticed?  Aside, OT is really evolved to be purposed for other uses - to put in kindly ... There's not much purpose in attempting much there.

It is not entirely disconnected.  Atmospheric aerosols that contribute to soil acidification - as just one example ... - are also connected to climate due to atmospheric microphysics and radiation budgeting... etc.  

Powered by a heatwave without precedent—christened “Heatwave Chevron” by former Weather Channel meteorologist Guy Walton—Phoenix experienced its hottest July and month on record. The dynamic city of 1.6 million spent day after day under a broiling sun in a raging storm of brutal, unforgiving, penetrating heat. Nights offered little relief from the fierce heat.

As a result, July 2023 left the prior hottest month, August 2020, in the dust much as Secretariat demolished the field in the 1973 Belmont Stakes. July 2023 surpassed the previous monthly mean temperature record by the largest margin by which any prior mark was surpassed. Phoenix also recorded the highest mean temperature and highest average low temperature for any month in any American city. The old records were a mean temperature of 102.2° and an average low temperature of 90.1° in Lake Havasu City during July 1996. Lake Havasu City also had an average high temperature of 114.4° during July 1996. Further, the lowest maximum temperature during July was 108°, which easily eclipsed the 104° mark from June 2013.

In addition to the records that melted under the unforgiving Phoenix sun, the 2023 heatwave produced Phoenix’s longest extreme heat event on record. Extreme heat events are determined using the Clarke et al., 2014 methodology, which applies percentiles to summer high temperature values from the 1971-2000 baseline. To qualify, a period must have at least three 115° or above high temperatures, an average high temperature of 115° or above for the duration of the extreme heat event, and no high temperatures less than 110° during the extreme heat event.

The Role of Climate Change

Anthropogenic climate change is driving a warming of Phoenix's summers. This ongoing warming is a global phenomenon with 98% of the world having experienced its warmest 51 years during the current 2,000 years. The IPCC’s Sixth Assessment Report found that heat and heatwaves are increasing on every continent. The primary driver is human-caused climate change. Phoenix’s unprecedented heatwave and record hot month are the result of a combination of factors that includes climate change, which has boosted temperatures and led to “stuck” patterns, the Urban Heat Island Effect, which has raised nighttime temperatures, and the synoptic pattern in which a powerful heat dome developed over the region.

The World Weather Attribution (WWA) Initiative found that the heatwave was “virtually impossible” without climate change and that temperatures were approximately 2°C (3.6°F) warmer on account of climate change. Event attribution studies calculate whether and the degree to which an event was made more (or less) likely and/or intense because of climate change.

The WWA warned, “Unless the world rapidly stops burning fossil fuels, these events will become even more common and the world will experience heatwaves that are even hotter and longer-lasting.” Heatwaves of the magnitude of the 2023 heatwave could occur every 2-5 years in a world that is 2°C (3.6°C) warmer than the pre-industrial world.

Summary

The record-setting summer of 2020 was a “summer from the future,” as it resembled the kind of summers that will likely occur on a regular basis by 2050. Similarly, the great 2023 heatwave can be said to be a “heatwave from the future.” On account of the unparalleled heatwave, July went on to become Phoenix’s hottest month on record, by far. In her poem, "Heatwave...Pleiades," Elizabeth Squires wrote of a heatwave "hotter than Hades... haranguing us from dusk to dawn." That was Phoenix in July 2023.

https://mailchi.mp/caa/groundhog-day-another-gobsmackingly-bananas-month-whats-up

Figure 4 includes our expectation that continuing record monthly temperatures will carry the 12-month temperature anomaly to +1.6-1.7°C. During subsequent La Ninas, global temperature may fall back below 1.5°C to about 1.4±0.1°C, but the El Nino/La Nina mean will have reached 1.5°C, thus revealing that the 1.5°C global warming ceiling has been passed for all practical purposes because the large planetary energy imbalance assures that global temperature is heading still higher.

The material in this thread is being copied over to American Weather Forum from its current location, the Net-weather forum in the UK. There will be one limitation in bringing the material here, namely, a smaller limit on attachment sizes will mean that links to supporting excel files created by myself will not be possible here. For those I may need to post links back to net-weather. I would just post that link in general but I wanted to create a second location where the data were accessible. Eventually I will also have an independent website to host this research. 

The thread was exclusively about the Toronto weather records for its first year of existence and then added NYC with comparisons to the Toronto data. So most of the second half of the thread is about the NYC data. If you start looking through this thread, at some point you may wonder where the NYC data is, so the answer is that it follows the posting of most of the Toronto data summaries. 

This is the thread that is now fully copied over to here:

https://www.netweather.tv/forum/topic/93113-toronto-180-a-north-american-data-base-of-180-years-now-includes-nyc-1869-2020/#comments

==========================================================

this is a link to the Alexis Caswell Providence RI weather journal. 

https://books.google.ca/books?id=oYY_AAAAcAAJ&printsec=frontcover#v=onepage&q&f=false

===========================================================

(introduction to net-weather thread posted there Jan 19, 2020. Note, edited the thread title on Net-weather recently as shown below)

Toronto-180 -- a North American data base of 185 years -- now includes NYC 1869-2025

I am now ready to post data from the Toronto-180 project. Toronto City is the current name of the weather station that operated as "Toronto" from 1840 to 2003. The location has always been somewhere around the modern-day University of Toronto campus which is located about 4 kms inland from Lake Ontario and near the northwest perimeter of the extensive central business district of the city (current metropolitan population 4.5 million). From 1840 to about 1880, the weather station was in a rural area on the outskirts of a much smaller community which grew to a population of about 10,000 when it began to surround the farmland where this weather station originally existed. (information added by edit on April 18) ... Although the station may have been near Fort York on the lakeshore briefly in 1840, it appears to have moved to the future site of the University of Toronto within a year or so, and until 1907 it was located where Kings College would eventually be situated, which nowadays is no longer an entity (the U of T has a number of colleges but this one no longer exists). That location was approximately 0.1 km southeast of Hart House in the central portion of the campus (now). Construction of University College nearby in the years 1906 to 1908 created so much dust and other disruption that it was decided to move the weather station, which included a geomagnetism observatory and a telescope, to a quieter location at the northwest margin of the campus, at 315 Bloor Street West, in a building that would later become the headquarters of the Dominion Weather Bureau, an antecedent of the modern day weather agency, Environment Canada (Meteorological Services). That headquarters functioned until 1971 when a new building was opened in suburban North York (Downsview), and the building in question has now become the admissions and bursary offices of the U of T.  (original text resumes) It was then (c.1908) moved about 1 km north to the former location of the headquarters of the "Dominion Weather Bureau" which became the Atmospheric Environment Service around 1969 and then Environment Canada in 1976. It was at that time that observations switched from the Imperial system to metric. The weather station was operated as a first-class reporting site for most of the years of its existence and has only recently been downgraded to a climatological station.

Around 2003, the instruments were moved away from the former headquarters building (at 315 Bloor St W, next to Varsity Stadium, at the north end of the campus), and placed in a suitable open grassy area near Trinity College about 0.3 km to the southeast. (again edited in, this final location is about midway between the original pre-1907 site and the subsequent 1908-2003 location and all are in similar terrain within a five minute walk of each other). The station name was then changed to "Toronto City." From 2003 to 2017, a separate observation program continued (under the name Toronto) recording only daily precip and snowfall. Meanwhile the Toronto City station recorded temperatures and daily precip, snow depths but no daily snowfall amounts. The purpose of the secondary station (which retained the name of the original) was to record snowfall and it only operated from mid-November to mid-April in most years (2003-17). It ceased to report in the 2017-18 winter season. The author has collected all data available and filled in a few observation gaps (most of them since 2013) from nearest possible locations well within the urban heat island. North York (located 13 km north) was preferred when available. These additional observations have changed some monthly mean temperatures and total precip values from published values slightly, as the practice of Environment Canada was to calculate means from available data unless a significant number of days were missing in which case no means or totals were assigned at all. In some cases, missing data was considerably different from the reported monthly mean and an adjustment was necessary. Most of the missing precipitation was (by luck of the draw) rather minor but one case was found where a heavy rainfall occurred on a missing date. All of these changes are logged in the excel file that is being developed. The temperature adjustments average out to almost zero (most changes to monthly means were of 0.1 or 0.2 C deg). 

The climate of Toronto is typical of eastern North America with large variations from month to month and day to day. There is a cold winter season that usually sets in around late November or early December and lasts to late February, March or in some cases early April. Snow can fall at any point from October to May (and traces have fallen in June and September). Snowfall is more reliable from early December to mid-March. But rain always falls during the winter season except in the coldest months each decade. Monthly rainfalls are fairly evenly distributed but year to year variations are very large. Monthly temperatures also vary by standard deviations of 3 or 4 C deg. The absolute range of monthly mean temperatures is 12-13 deg in winter and 5-6 deg in summer. A hot and rather humid summer season makes a few appearances in May and early June, then often sets in with a few cooler interludes for most of July and August. September tends to be warm and less humid in most years, and there is often a considerable change to autumnal weather around the equinox. October is either a pleasant "Indian summer" regime or in some years a windy and cool month with mixed wintry showers at times. 

This thread will document all aspects of the Toronto climate in the same style that I adopted for the CET studies in the historical weather section (over on net-weather). Although it might be appropriate to post it there, it also has climate change implications. Toronto is probably a good proxy for the eastern North American climate in general. Its extremes tend to be of similar magnitude and timing to those experienced in the eastern U.S. and if a month is very warm or very warm at Toronto, chances are high that it will also be that way in Chicago, New York, Washington and Boston (and most points in between). Anomaly patterns in eastern North America tend to have the shape and extent of typical large highs and lows that move through the region on a regular basis. Some details of this correlation are examined in more detail when we get to the NYC portion of this study.

There are a few local effects worth noting. A strong cooling lake breeze can blow in during settled periods in the spring, and drop temperatures by 5-10 C deg relative to more inland locations. Some research indicates that the development of a large city with tall buildings closer to the lakeshore can inhibit this lake breeze, and this may be a factor in assessing how cool springs and early summers were in the 19th century. A weather journal taken in Providence RI has evidence of a blistering heat wave in July 1849 (highs of 97 F were noted) that translated to rather subtle warmth at Toronto (highs 85-90), and from experience I would say that in a modern climate setting that difference might have been reduced by several degrees. The urban heat island probably grew fastest for this location around 1900 to 1930. I have assessed its strength overall at a conservative 1.1 C deg averaged over all types of weather, and as large as 4-6 C deg on cool, clear nights. It might seem larger to a casual observer, but rural stations outside the urban heat island are also at a higher elevation and would have a cooler temperature regime than the Toronto city location even without the presence of the large city. Wind speeds over 30 km/hr tend to reduce the urban heat island. Cloud and rainfall also tend to reduce it considerably. Eventually I will publish tables of temperature rankings and supplement those with adjusted temperatures for urban heat island (as the CET managers are doing), taking off 1.1 C from readings since 1981, 1.0 for those 1971-1980, 0.9 for 1961-70, 0.8 for 1951-60, 0.7 for 1941-50, 0.6 for 1931-40, 0.5 for 1921-30, 0.4 for 1911-1920, 0.3 for 1901-1910, and 0.2 for data 1891 to 1900, 0.1 for 1881 to 1890. This should make the urban effect less of an advantage to later years in comparison. The warming since around the 1880s has been considerably larger than 1.1 C and at a faster pace in the early part of the urban development. There would always be a possibility of revising the urban heat island correction. But in general terms, I believe that the modern warming of the climate is about an equal combination of natural variability augmented by the AGW signal, plus the urban heat island. Some ask, isn't the urban heat island part of the AGW signal? Not really, the mixing of greenhouse gases into the free atmosphere is not confined to urban areas although it might largely originate there, whereas the urban heat island is specific to the urban setting and when the surplus heat is dissipated by stronger winds, the net effect on global temperatures is smaller than the AGW signal (by a factor of about 1:10). So you could perhaps say that the urban heat island dissipation cycle is something like 10 per cent of the AGW warming signal. 

The research file logs all record highs and lows in temperatures, and record high rainfalls and snowfalls. Tables will appear in this thread to summarize all of that. Eventually the research (excel) file can be shared but as the station did not open until March 1st of 1840, the "Toronto-180" project will not be complete until March 1st of this year. So I probably won't publish the file until we pass that point and I can insert values for January 2020 and February 2020 into the tables. (later edit _ as I am now adding some precip data to the excel files, those won't be fully available until May or June 2020, but the work is essentially complete as of April 2020 on the originally proposed Toronto 180 project, and this thread is the record of that).

I will start the process with the average monthly temperatures and annual means (unadjusted for urban heat island). This may take an edit or two as it looks orderly on my screen but may not look that orderly on the post. Then I will post some shells of other tables to reserve space before any comments begin to appear. Please refrain from commenting for at least a day or two until I have these posts in place. I will fill them out as quickly as possible in the coming days. 

Note on metric conversion ... Canada adopted the metric system around 1976, but these files converted on June 1, 1978. Before that date, all of the values shown in the historical data internet files from source (Environment Canada) are exclusively Fahrenheit to Celsius conversion values. Starting on June 1, 1978, new values that do not occur in that conversion protocol appear (for example, max temp June 1 1978 is 22.0, for 72 F the value reported is always 22.2; the first metric rainfall observation was 0.2 mm, whereas the only choices available for Imperial unit conversion were 0.0 and 0.3 mm for 0.01" -- so while it's possible that the conversion started in May with the coincidence of all values happening to conform to conversion protocols, it seems most likely that the switch to metric in recording this station's data came on June 1, 1978.)

Work is ongoing to provide all the same data tables for NYC (New York City Central Park), a station that opened near its current location in 1869 in mid-town Manhattan and has a similar parkland setting to the downtown Toronto site. To date all of the same temperature tables except daily records have been posted. 

Meanwhile the author has finished an excel file for the Toronto data including all precip data and plans to make this available at the end of 2020 once the December 2020 data are inserted into the files here (and there). 

NYC precip data are coming along too, Don Sutherland of American Weather Forum has kindly assisted me with provision of data sets in excel table format and eventually I will have that ready for sharing with climate researchers. Much of the NYC data can be easily accessed on the NWS New York City home page too. 

Research Links Climate Change to Lazier Jet Stream, Leading to Extreme Weather

BY COLUMBIA CLIMATE SCHOOL |JULY 14, 2023

 

 Comments

Jet streams are relatively narrow bands of strong wind in the upper atmosphere, typically occurring around 30,000 feet, and blowing west to east. Their normal flows lead to week-to-week weather variations, modulated in the mid-latitudes by ridges and troughs in the jet stream. A high-pressure ridge, for example, produces clear, warmer weather conditions; a trough is typically followed by stormy conditions. Together, these form waves in the jet stream that can stall as the waves grow and become more amplified, causing “stuck” weather patterns that produce longer storms and heat waves.

New research published in Nature Communications describes observations linking increased warming at high latitudes and the ever-decreasing snow cover in North America to these stalls in atmospheric circulation.

“These persistent and extreme conditions are thought to be increasing in the future as a result of this increased waviness in the jet stream.” said the study’s lead author Jonathon Preece, a postdoctoral researcher at the University of Georgia.

High-pressure ridge over Texas, 2018. (Weatherbell)

Since 2000, frequent “stuck” weather patterns have produced heat waves over Greenland, resulting in exceptional melting of the Greenland Ice Sheet. In contrast to these observations, global climate models actually project a slight decrease in the blocked patterns over Greenland and, consequently, the models have underrepresented the contribution of meltwater runoff from the ice sheet to global sea level rise.

“These patterns have been consistently creating pulses of melting over the Greenland ice sheet that have been accounting for a large portion of the annual melting,” said study coauthor Marco Tedesco, a professor at Columbia Climate School’s Lamont-Doherty Earth Observatory, and lead principal investigator on the project. “Accounting for such an aspect is crucial for anticipating not only how much but how fast Greenland is and will be contributing to sea level rise.”

“One question is whether this is a consequence of climate change that we can expect to continue in the future [that] the climate models are failing to resolve,” said Preece. “Or are the climate models correct, in which case we’d expect things to revert back to the norm and perhaps the rate of accelerated melt of the ice sheet will taper some?”

The new study presents evidence of a link to climate change, both in the increases in jet-stream waviness and ever-decreasing spring North American snow cover extent,  which “is impacting the atmosphere in a way that is favoring these blocked high-pressure systems over Greenland,” Preece said.

Multiple studies have highlighted the discrepancy between climate models and observations. This study provides evidence of a direct connection between the observed shift in summer atmospheric circulation over Greenland and amplified warming at high latitudes.

“The new study is the first that we know of that demonstrates a direct link between the observed change in summer atmospheric circulation over Greenland and diminished spring snow cover, which is something we can confidently say is a consequence of climate change,” said coauthor Thomas Mote, a geographer at the University of Georgia.

Adapted from a press release by the University of Georgia.

Full paper available online with no paywall.
 

https://www.nature.com/articles/s41467-023-39466-6

Abstract

Let's take a quick look. Neither Wielicki nor Martz has sufficient understanding of weather and climate to analyze what has actually taken place. Instead, both push the common fallacy that rainfall in the past (last 20 winters, in this case) means there can't possibly be a drought, much less severe wildfire conditions.

Now the facts:

1. Los Angeles County is in the midst of a moderate or severe drought, as is much of southern California. Moreover, drought conditions were growing rapidly worse. The latest data:

2. Rainfall in past winters means nothing. That rainfall is in the distant past. What matters is how much rain has recently fallen. Many locations have had either their second lowest or lowest rainfall on record since June 1. Through yesterday, Blythe has gone a record 282 consecutive days without measurable rainfall. Lancaster has gone 238 consecutive days without measurable rainfall (second longest such streak).

3. Flash droughts, which can develop in as few as five days are becoming increasingly frequent due to climate change. Two papers:

A global transition to flash droughts under climate change

Global projections of flash drought show increased risk in a warming climate

Increased risk of flash droughts with raised concurrent hot and dry extremes under global warming

4. Climate change is also driving an increase in the vapor pressure deficit leading to more intense and extreme wildfires. One paper:

Quantifying contributions of natural variability and anthropogenic forcings on increased fire weather risk over the western United States

5. The literature has made abundantly clear that climate change is leading to an increased wildfire risk in southern California. A key paper:

The season for large fires in Southern California is projected to lengthen in a changing climate

Two Key Points:

1. Neither person cited in the opening has the background knowledge or information to make an informed judgment about weather, climate, or the antecedent conditions responsible for southern California's catastrophic wildfires. Their reasoning about past precipitation was fallacious. Both had no idea that the region was currently in a drought or any awareness that drought products exist and can readily be accessed by the public. They appear to have no knowledge of the concept of flash droughts, thus there flawed argument about past winters' rainfall. They are unfamiliar with the literature on  the role of climate change in driving flash droughts, increased vapor pressure deficits, and on the wildfire risk to southern California.

2. At a time of great danger and terrible tragedy, such ill-informed social media accounts should refrain from pushing disinformation, if just for ethical reasons. Their misleading people--including those at risk of the wildfires or victims of the fires--can put lives at risk. It can also increase the emotional distress being experienced among those who have already lost much in the raging fires.

Summer 2024 got off to a blazing start with its hottest June, by far, on record. The sizzling June was followed by Phoenix’s second hottest July and second hottest month on record. July featured an 11-day extreme heat event (Clarke et al., 2014 methodology) during which the temperature reached or exceed 115° on six days. That was the second longest such event on record. Summer concluded with the third hottest August on record.

On account of the historic heat, Phoenix saw its longest stretches of 80° or above lows, 100° or above highs, and 105° or above highs:

• 80° or above lows: 74 days, June 5-August 17; old record: 51 days, July 1-August 20, 2023
• 100° or above highs: 97 days (as of August 31 and ongoing); old record: 76 days, June 10-August 24, 1993
• 105° or above highs: 63 days, June 5-August 6; old record: 56 days, June 24-August 18, 2023

Anthropogenic climate change amplified by the urban heat island effect is driving a warming of Arizona’s and Phoenix's summers. Data from a joint May 2024 report published by Climate Central, Red Cross Red Crescent Climate Centre and World Weather Attribution revealed that the influence of climate change has resulted in a 231.1% increase in Arizona’s days with temperatures above the 90^th percentile (1991-2020 baseline) over the figure expected without the influence of climate change.

The warming has accelerated in recent decades. Between 1950 and 2023, summers have warmed by 0.6° per decade in Phoenix. Since 1980, summers have warmed by 0.9° per decade. As a result, Phoenix has set summer records in 2020, 2023, and now 2024. As a result, the annual number of days on which the high temperature has exceeded the 90^th percentile for summer maximum readings (1991-2020 baseline) has increased from 6.5 days during 1961-1990 to 9.99 days during 1991-2020. The most recent 30-year moving average (1995-2024) is 12.7 such days per year (through August 31, 2024).

Select highlights:

Updates:

Phoenix records 100th 80° low temperature of the year

Progression of Phoenix's Record Streak of 100° Highs

Phoenix and Surrounding Area 100° Highs and 80° Lows

U.S. Sites with 110 or More Consecutive 100° Highs and Population

Hottest Last 7 Days of September

Phoenix Experiences its Hottest September on Record

Phoenix's Extreme September 28th and October 1st High Temperatures

Phoenix Experiences its Hottest First Week of October on Record

Phoenix Sets or Ties Daily High Temperature Records on an Unprecedented 21 Consecutive Days

Climate Change not the Urban Heat Island Effect drove Phoenix's Record Autumn Heatwave

Southwest Region Summer Trends

Phoenix Follows its Hottest Summer with its Warmest Fall on Record

Phoenix Caps Off its Warmest Year with Its Warmest December on Record

Summer 2024 got off to a blistering start with its hottest June on record. July became that City’s hottest month on record. August also became its hottest August on record.

July featured a 12-day extreme heat event (Clarke et al., 2014 methodology) during which the temperature reached or exceed 115° on a record seven consecutive days. That extreme heat event was highlighted by Las Vegas’ hottest reading on record (120°) and three other temperatures that surpassed the old all-time mark of 117°.

On account of the historic heat, Las Vegas saw its longest stretches of 80° or above lows, 105° or above highs, 110° or above highs, and 115° or above highs:

• 80° or above lows: 63 days, June 21-August 22; old record: 33 days, July 4-August 5, 2020
• 105° or above highs: 43 days, June 20-August 1; old record: 25 days, June 15-July 9, 2017
• 110° or above highs: 11 days, July 3-13; old record: 10 days, June 17-26, 1961 and July 14-23, 2023
• 115° or above high: 7 days, July 6-12; old record: 4 days, July 16-19, 2005

Anthropogenic climate change amplified by the urban heat island effect is driving a warming of Las Vegas’ summers. The warming has accelerated in recent decades. Between 1950 and 2023, summers have warmed by 0.8° per decade in Las Vegas. Since 1980, summers have warmed by 1.0° per decade.

Select highlights:

Anthropogenic climate change is driving a warming of Phoenix's summers. It is making hot patterns hotter. Hot nights are amplified by the Urban Heat Island (UHI) Effect. Climate change is also increasing the persistence of hot patterns through wave resonance events. The observed global warming since the 1950s is unequivocal with anthropogenic greenhouse gas emissions, largely from the burning of fossil fuels, being the dominant driver of that warming.

Phoenix’s full-year records go back to 1896. The first summer to average 95.0° or above occurred in 2013 (95.1°). Summer 2015 matched the 2013 record. Summer 2020, which set a record for most 100° days (145) set a new benchmark at 96.7°. Three years later, that mark was incinerated by a 97.1° average summer temperature. Since 1980, Phoenix’s summers have been warming at a rate of 0.9° per decade.

June is also warming rapidly. The monthly mean temperature has increased 3.2° from the 1961-1990 period to the 1991-2020 period. June 2006 was the first June to attain a mean temperature of 94.0° or above (94.6°). That mark was then broken in 2013 (94.8°) and 2021 (95.3°). The 2021 record was demolished this year.

Since 2015, six of the ten Junes have had a monthly mean temperature of 94.0° or above. Put another way, June heat that was once extraordinary is now on a path toward becoming normal.

Select Highlights:

Updates:

Phoenix's warming summers

Phoenix Experiences its Hottest Summer on Record

https://www.science.org/content/article/america-s-corn-belt-making-its-own-weather

The United States’s Corn Belt is making its own weather

By Kimberly HickokFeb. 16, 2018 , 12:05 PM

The Great Plains of the central United States—the Corn Belt—is one of the most fertile regions on Earth, producing more than 10 billion bushels of corn each year. It’s also home to some mysterious weather: Whereas the rest of the world has warmed, the region’s summer temperatures have dropped as much as a full degree Celsius, and rainfall has increased up to 35%, the largest spike anywhere in the world. The culprit, according to a new study, isn’t greenhouse gas emissions or sea surface temperature—it’s the corn itself.

This is the first time anyone has examined regional climate change in the central United States by directly comparing the influence of greenhouse gas emissions to agriculture, says Nathan Mueller, an earth systems scientist at the University of California (UC), Irvine, who was not involved with this study. It’s important to understand howagricultural activity can have “surprisingly strong” impacts on climate change, he says.

The Corn Belt stretches from the panhandle of Texas up to North Dakota and east to Ohio. The amount of corn harvested in this region annually has increased by 400% since 1950, from 2 billion to 10 billion bushels. Iowa leads the country for the most corn produced per state.

To see whether this increase in crops has influenced the region’s unusual weather,researchers at the Massachusetts Institute of Technology in Cambridge used computers to model five different 30-year climate simulations, based on data from 1982 to 2011. First, they compared simulations with high levels of intense agriculture to control simulations with noagricultural influence. Unlike the real-life climate changes, the control simulations showed no change in temperature or rainfall. But 62% of the simulations with intense agriculture resulted in temperature and rainfall changes that mirror the observed changes, the team reports this week in Geophysical Research Letters.

The team then compared its results to historical global simulations from the World Climate Research Programme (WCRP), an international program for the coordination of global climate research sponsored by the International Council for Science, the World Meteorological Organization, and the Intergovernmental Oceanographic Commission of UNESCO. WCRP’s models take into account greenhouse gas emissions and other natural and humanmade influences, but do not consider agricultural land use. When researchers ran the numbers for the Corn Belt, the global models fell short of reality: They predicted both temperature and humidity to increase slightly, and rainfall to increase by up to 4%—none of which matches the observed changes.

Other climate simulations that use sea surface temperature variation didn’t match observed changes, either. Those simulations matchedhistorical data until 1970; after that, the simulations predicted temperatures to keep increasing, rather than decreasing as they did in reality. This is a strong indication that agriculture, and not changing sea surface temperature, caused the regional changes in climate during the last third of the 20th century, the researchers say.

“The [influence] of agriculture intensification is really an independent problem from greenhouse gas emissions,” says Ross Alter, lead author of the study and now a meteorologist with the U.S. Army Corps of Engineers in Hanover, New Hampshire. In fact, Alter says, heavy agriculture likely counteracted rising temperatures regionally that might have otherwise resulted from increasing greenhouse gas emissions. One other place that shows a similar drop in temperatures, he notes, is eastern China, where intensive agriculture is widespread.

But how does agriculture cause increased rainfall and decreased temperatures? The team suspects it has to do with photosynthesis, which leads to more water vapor in the air. When a plant’s pores, called stomata, open to allow carbondioxide to enter, they simultaneously allow water to escape. This increases the amount of water going into the atmosphere and returning as rainfall. The cycle may continue as that rainwater eventually moves back into the atmosphere and causes more rainfall downwind from the original agricultural area.

Rong Fu, a climate scientist at UC Los Angeles, agrees with the team’s assessment. She alsothinks that though human influence might be “greater than we realize,” this regional climate change is probably caused by many factors,including increased irrigation in the region.

“This squares with a lot of other evidence,” says Peter Huybers, a climate scientist at Harvard University, who calls the new study convincing. But he warns that such benefits may not last if greenhouse gas emissions eventually overpower the mitigating effect of agriculture.

Alter agrees, and says it’s unlikely that the large increases in U.S. crop production during the 20th century will continue. Other scientists have voiced concern that agricultural production could soon be reaching its limit in many parts of the world. 

“Food production is arguably what we’re more concerned about with climate change,” Mueller says. And understanding how agriculture and climate will continue to affect one another is crucial for developing projections for both climate and agricultural yields. “It’s not just greenhousegasses that we need to be thinking about.” 


https://news.wisc.edu/irrigated-farming-in-wisconsins-central-sands-cools-the-regions-climate/
 

New research finds that irrigated farms within Wisconsin’s vegetable-growing Central Sands region significantly cool the local climate compared to nearby rain-fed farms or forests.

Irrigation dropped maximum temperatures by one to three degrees Fahrenheit on average while increasing minimum temperatures up to four degrees compared to unirrigated farms or forests. In all, irrigated farms experienced a three- to seven-degree smaller range in daily temperatures compared to other land uses. These effects persisted throughout the year.

The results show that the conversion of land to irrigated agriculture can have a significant effect on the regional climate, which in turn can affect plant growth, pest pressure and human health in ways that could be overlooked unless land uses are accounted for in forecasts and planning.

Such a cooling effect mitigates — and obscures — a global warming trend induced by the accumulation of greenhouses gases in the atmosphere. Irrigated farming, like all agriculture, also generates greenhouses gases.

The work was led by Mallika Nocco, who recently completed her doctorate in the Nelson Institute for Environmental Studies at the University of Wisconsin–Madison. Nocco worked with Christopher Kucharik of the Nelson Institute and the UW–Madison agronomy department and Robert Smail from the Wisconsin Department of Natural Resources.

The team published their findings July 2 in the journal Global Change Biology.

“We’re finding that weather forecasts can be wrong if they don’t take these land uses into account,” says Nocco, now a postdoctoral researcher at the University of Minnesota. “That will affect both farmers and plants.”

Irrigation, and agriculture generally, cools the air due to the evaporation of water through crop leaves, much like how evaporating sweat cools people. This evaporation also increases the water content of the air. The scientists wanted to determine if the naturally humid Wisconsin climate would respond as strongly to irrigation as drier regions, such as California, do.

To find out, Nocco worked with private landowners to install 28 temperature and humidity sensors in a line that crossed through the Central Sands. The 37-mile transect extended from pine plantations in the west, over irrigated farms toward forests in the east. The researchers collected data across 32 months from the beginning of 2014 through the summer of 2016.

Each of the 28 sensors was matched to nearby irrigation levels through a regional well withdrawal database managed by Smail of the Department of Natural Resources.

Nocco’s team found that irrigation lowered the maximum daily temperature about three and half degrees compared to nearby rainfed farms. Adjacent forests were slightly warmer than either rainfed or irrigated farms.

Somewhat surprisingly, the lower maximum temperatures on irrigated farms were accompanied by higher minimum temperatures. Saturated soils can hold more heat than dry soils. When that heat is released at night, it keeps nighttime minimum temperatures somewhat higher. Wet soils may also be darker, helping them absorb more sunlight during the day.

The researchers found that if all land in the study area were converted to irrigated agriculture, the daily range in temperatures would shrink nearly five degrees Fahrenheit on average, and up to eight degrees at the high end. This smaller difference between daily maximum and minimum temperatures can significantly affect plant growth or insect pest lifecycles, both of which are sensitive to daily temperatures.

“If you’re adjusting the range of temperatures, you’re changing who or what can live in an area,” says Nocco.

The temperature differences between irrigated fields and rain-fed fields or forests were pronounced during the growing season, when fields were being irrigated, but extended throughout the year. Open fields of snow reflect more winter sunlight than forests do, keeping the air above cooler, but it’s not entirely clear what drives winter temperature differences between irrigated and non-irrigated farms.

While the cooling effect of irrigation mitigates global climate change on the regional scale, climate models suggest that regional warming attributed to the global trend will eventually overcome the magnitude of mitigation offered by irrigated agriculture. Farmers, who are partially buffered for now from more extreme heat, would quickly face increasing stress in that scenario.

“Farmers in irrigated regions may experience more abrupt temperature increases that will cause them to have to adapt more quickly than other groups who are already coping with a warming climate,” says Kucharik. “It’s that timeframe in which people have time to adapt that concerns me.”

The current study is the first to definitively link irrigation in the Midwest U.S. to an altered regional climate. These results could improve weather and climate forecasts, help farmers plan better, and, the researchers hope, better prepare agricultural areas to deal with a warming climate when the irrigation effect is washed out.

“Irrigation is a land use with effects on climate in the Midwest, and we need to account for this in our climate models,” says Nocco.

This work was supported in part by the U.S. Environmental Protection Agency, the U.S. Department of Agriculture Sustainable Agriculture Research and Education program and the Wisconsin Department of Natural Resources.

https://www.nature.com/articles/s41467-020-16676-w

The severe drought of the 1930s Dust Bowl decade coincided with record-breaking summer heatwaves that contributed to the socio-economic and ecological disaster over North America’s Great Plains. It remains unresolved to what extent these exceptional heatwaves, hotter than in historically forced coupled climate model simulations, were forced by sea surface temperatures (SSTs) and exacerbated through human-induced deterioration of land cover. Here we show, using an atmospheric-only model, that anomalously warm North Atlantic SSTs enhance heatwave activity through an association with drier spring conditions resulting from weaker moisture transport. Model devegetation simulations, that represent the wide-spread exposure of bare soil in the 1930s, suggest human activity fueled stronger and more frequent heatwaves through greater evaporative drying in the warmer months. This study highlights the potential for the amplification of naturally occurring extreme events like droughts by vegetation feedbacks to create more extreme heatwaves in a warmer world.

https://news.ucar.edu/132872/1930s-dust-bowl-affected-extreme-heat-around-northern-hemisphere
 

The 1930s Dust Bowl, fueled by overplowing across the Great Plains and associated with record heat and drought, appears to have affected heat extremes far beyond the United States.

New research finds that the hot, exposed land in the central U.S. during the Dust Bowl drought  influenced temperatures across much of North America and as far away as Europe and East Asia. That’s because the extreme heating of the Great Plains triggered motions of air around the Northern Hemisphere in ways that suppressed cloud formation in some regions and, in combination with the influence of tropical oceanic conditions, led to record heat thousands of miles away.

“The hot and dry conditions over the Great Plains during the Dust Bowl spread extreme heat to other areas of the Northern Hemisphere,” said Gerald Meehl, a scientist with the National Center of Atmospheric Research (NCAR) and lead author of the new study. “If you look at daily record high temperatures, some of these areas are just now breaking the records that were set in the 1930s.”

To determine the climatic impact of the Dust Bowl, the research team drew on observed high and low daily temperatures, as well as advanced computer models of the global climate system. They focused on the role of a teleconnection pattern, known as wave-5, that can regulate the meandering of jet streams and link far-flung weather patterns around the Northern Hemisphere during summer.

The study was published in Scientific Reports. It was funded by the U.S. National Science Foundation, which is NCAR’s sponsor, as well as by the U.S. Department of Energy.

TEASING OUT THE DUST BOWL’S INFLUENCE

The Dust Bowl is widely viewed as one of the nation’s worst environmental disasters. Farmers in the early part of the 20th century plowed up millions of acres of native grassland across much of the Great Plains to plant wheat and other crops. When a multiyear drought struck in the 1930s, the exposed land became exceptionally hot and topsoil blew away, causing devastating dust storms as well as a health and economic catastrophe.

The new research points out that extreme weather conditions extended far beyond the immediate vicinity of the Dust Bowl. Much of North America, northern Europe, and eastern and northeastern Asia experienced such heat that some record high temperatures of the 1930s are only now being exceeded as temperatures rise with climate change.

Previous research pointed to patterns of warm and cool surface temperatures in the tropical oceans as triggering the drought in the Great Plains. These conditions were associated with a pair of multidecadal phenomena known as the Interdecadal Pacific Oscillation (IPO) and Atlantic Multidecadal Oscillation (AMO). The question addressed by Meehl and his co-authors was whether such oceanic conditions could also explain the hot and dry weather around so much of the Northern Hemisphere, or if the Dust Bowl itself played a role.

To tease out the influence of the Dust Bowl, the scientists first used an NCAR-based model of global climate, known as the Community Earth System Model (CESM). They ran a series of simulations on the Cheyenne supercomputer at the NCAR-Wyoming Supercomputing Center to see whether the IPO and AMO could fully account for the distribution of extreme daily high temperatures across three continents. But even though they set the model to capture the likely oceanic conditions of the time, they could not reproduce the high daily temperatures of the 1930s.

They then turned to a version of the CESM atmospheric model that is a component of the DOE Energy Exascale Earth System Model, and set the model to isolate the influence of the extreme heat over the Great Plains during the 1930s. This time the results closely matched actual climate records, indicating that the Dust Bowl generated an atmospheric reaction that, in combination with conditions in the tropical Pacific and Atlantic, triggered extreme heat across vast areas of the Northern Hemisphere.

“When you put the influence of the Great Plains Dust Bowl drought in the model, you get record-breaking heat in the areas where we saw them in the Northern Hemisphere during the 1930s,” Meehl said.

INFLUENCE OF WAVE-5

Additional analysis of the simulations revealed the reason the Dust Bowl had such a pronounced effect on other regions: it generated a series of far-reaching vertical motions in the atmosphere. Such movements are known as a wavenumber-5 or wave-5 teleconnection — so named because it consists of five pairs of alternating high- and low-pressure features that encircle the globe along jet streams.

In this case, the intense surface heating of the Great Plains created an upward motion of warm air, which then moved downward in surrounding areas, suppressing the formation of clouds over much of the northern U.S. and Canada. It also produced sinking air that suppressed clouds in other regions around the Northern Hemisphere, allowing more sunlight to reach the surface and resulting in soaring temperatures. At the same time, the pattern enabled warm, southerly winds to reach as far north as Scandinavia and eastern Asia. These winds contributed to the extreme heat over much of northern Europe and parts of eastern Asia.

Meehl said the study helps illuminate how conditions on one part of the planet can affect the atmosphere thousands of miles away. Scientists have long known about the climatic influence of the vast tropical oceans, which pump out enormous amounts of relatively moist, warm air affecting weather patterns worldwide, as with El Niño. But it has proven more difficult to tease out linkages that arise from conditions over smaller areas of land in the midlatitudes, especially during summer.

“This is a mechanism that arose in a unique way from human influence — not by burning fossil fuels but from plowing up the middle third of the U.S.,” Meehl said. “It’s possible that intense regional droughts in the future could also influence heat extremes in the Northern Hemisphere.”

On Monday, the most populated region in the Pacific Northwest could see widespread temperature anomalies more than 4 standard deviations above the normal figures. A small part of the region could experience temperatures more than 6 standard deviations above normal.

Standardized Temperature Anomalies (6/28 18z):

Select June, All-Time Records, Forecast Maximum Temperatures:

Western sections of Oregon, Washington, and British Columbia, including Portland, Seattle, and Vancouver, will likely see the highest temperatures during the June 26-29 period. Elsewhere, exceptional warmth could persist into the opening days of July.

Minimum temperatures will also approach monthly and all-time lows, especially in areas affected by the Urban Heat Island (UHI) effect, namely Portland, Seattle, and Vancouver.

Climate change is increasing the frequency, magnitude, and duration of extreme heat events. One important mechanism is through wave resonance events (Mann et al., 2017). If one steps back to a larger hemispheric perspective starting near the beginning of June, one has witnessed the emergence of mega-heat domes in a "whack-a-mole" fashion in the Northern Plains, Southwest,  and northern and eastern Europe (including northwestern Russia) that led to record heat, including some monthly or all-time record high temperatures. This latest heat dome is the fourth such major event this month.

Updates:

Recurrent Rossby Waves, Heatwaves, and Climate Change

June 27, 2021: New Canadian National High Temperature Record

June 28, 2021: New Canadian National High Temperature Record

June 29, 2021: New Canadian National High Temperature Record

Unprecedented North American Heatwave Scorches the Pacific Northwest

Historic Nature of the Heatwave 

Attribution Study: 'Virtually Impossible' without Climate Change

https://www.disl.edu/about/news/marine-heatwaves-and-hurricanes-study-examines-compounding-impact-of-severe-weather

Several coastal communities are picking up the pieces after being ravaged by hurricanes in the past month. Hurricane Laura, a category 4, and Hurricane Sally, a category 2, seemed to meander their way across the Gulf of Mexico constantly shifting forecasts and keeping meteorologists on their toes. In the hours before these storms struck land, they seemed to explode in intensity. 

Researchers at the Dauphin Island Sea Lab with support from the Jet Propulsion Laboratory can offer insight into why these storms intensified quickly as they moved across the continental shelf. 

“Surprisingly, both Hurricane Laura and Hurricane Sally appeared to have similar setups to Hurricane Michael with both storm events being preceded by smaller storms (i.e. Hurricane Hanna and Marco, respectively),” Dr. Brian Dzwonkowski explained. “This pre-storm setup of the oceanic environment likely contributed to the intensification prior to landfall.  Importantly, this pre-landfall intensification was not well predicted by hurricane models or forecasts, which as you can imagine is critical information for evacuation  and disaster preparation.”

Dzwonkowski and his team’s publication, “Compounding impact of severe weather events fuels marine heatwave in the coastal ocean”, outlines how one storm could impact the intensity of another storm by restructuring the thermal properties of the water column. Nature Communications published the findings in its September issue.

The research focuses on Hurricane Michael which devastated Mexico Beach, Florida, and the surrounding communities, on October 10, 2018. The category 5 storm intensified hours before making landfall. 

Dzwonkowski, a physical oceanographer with the Dauphin Island Sea Lab and Associate Professor at the University of South Alabama in the Department of Marine Sciences, and his team tracked down the key events and processes that pushed the coastal waters in the Gulf of Mexico to an extremely warm state (i.e. a marine heatwave), likely contributing to the intensification of a storm so close to shore. 

Unlike the deep ocean, the continental shelf has a shallow bottom that limits how much cold water can be mixed up to the surface, cooling the sea surface temperature and weakening approaching storms. Dzwonkowski and his team focused on how a strong mixing event pushes surface heat downward and clears the bottom water of its cold water reserve.  If this mixing is followed by a period of rewarming, such as an atmospheric heatwave,  the shelf’s oceanic environment could be primed for the potential generation of extreme storm events, i.e. Hurricane Michael.

This work shows that understanding the preceding weather conditions in a region where a storm is going to make landfall can improve interpretation of hurricane model forecasts  and what the storm is likely to do prior to landfall,” says Dr. Dzwonkowski 

In mapping out heat flux and mixing, the team focused on the Mississippi Bight in late summer and early fall with data gathered by a mooring site off Dauphin Island’s coastline. The mooring site collects data throughout the water column allowing for the full heat content of the shelf to be determined. The period prior to the landfall of Hurricane Michael turned out to be the warmest ocean conditions during this time period in the 13-year record. 

 “Turns out hurricanes and atmospheric heatwaves will be getting stronger in a warming world which would indicate the identified sequence of events that generate these extreme conditions may become more frequent,” Dzwonkowski said.   “The occurrence of extreme heat content events, like marine heatwaves has significant implications for a broad range of scientific management interests beyond hurricane intensity.”Importantly, the mechanisms that generated this marine heatwave are expected to be more frequent and intense in the future due to climate change, increasing the likelihood of such extreme conditions.  

For example, coral reefs and hypoxia-prone shelves are already stressed by long-term warming trends. These temperature-specific benthic communities and habitats are typically of significant societal and economic value. As such, the newly identified sequence of compounding processes is expected to impact a range of coastal interests and should be considered in management and disaster response decisions. 

This research was funded by the NOAA RESTORE Science Program and NOAA NGI NMFS Regional Collaboration network. 

https://www.nature.com/articles/s41467-020-18339-2

Abstract