donsutherland1

Morning thoughts... At 8:45 am, a shrinking area of moderate to heavy rain that had brought 0.66" rain to Wilmington was headed northward toward Allentown. Much of the rest of the region was cloudy with a few widely scattered light showers. Today will be mainly cloudy with perhaps a few additional showers. The sun could begin to break through the clouds during the afternoon. Temperatures will likely reach the lower to perhaps middle 70s across the region. Likely high temperatures around the region include: New York City (Central Park): 74° Newark: 75° Philadelphia: 75° The temperature will likely remain above normal through the remainder of the month.

@blizzard1024Tree rings at some locations had seemingly become a less reliable indicator of temperature. More recent research suggests that light (dimming) may have been responsible. https://phys.org/news/2014-05-arctic-tree-ring-divergence-problem.html

I’m not sure if the below paper has been posted here, but it allows for comparisons of Arctic sea ice volume during the first half of the 20th century, including the 1920-40 Arctic warming, and the rapid declines in volume today. The paper is: Arctic Sea Ice Volume Variability over 1901–2010: A Model-Based Reconstruction https://journals.ametsoc.org/jcli/article/32/15/4731/343909/Arctic-Sea-Ice-Volume-Variability-over-1901-2010-A

If the use of proxy data is the “weakest link,” how would you go about trying to compare today’s temperatures with those during the rest of the Holocene?

Tomorrow will be mainly cloudy with perhaps a few showers and a little cooler than today. In general, temperatures will likely remain at generally above normal levels for the remainder of September. A cool shot is possible in the opening week of October, but warmer readings could return during the following week. Phoenix has an implied 90% probability of recording just its 13th September on record with a mean temperature of 90° or above. The most recent such occurrence was 2018 with a mean temperature of 91.8°. Phoenix will very likely record its hottest June-September period on record with a four-month mean temperature of near 95.3°. That would exceed the previous June-August record of 95.1°, which was set in 2013 and tied in 2015. The existing record is 93.9°, which was set in 2011. The ENSO Region 1+2 anomaly was -0.4°C and the Region 3.4 anomaly was -0.8°C for the week centered around September 16. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.93°C and the ENSO Region 3.4 anomaly has averaged -0.68°C. La Niña conditions have developed and will likely prevail through the remainder of autumn. The SOI was +16.88. Today, the preliminary Arctic Oscillation (AO) figure was +0.613. On September 24, the MJO was in Phase 5 at an amplitude of 1.436 (RMM). The September 23-adjusted amplitude was 1.370. Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. Based on sensitivity analysis applied to the latest guidance, there is an implied 79% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.6°.

The American Meteorological Society (AMS) just published the state of the climate report for 2019. Excerpts: All major greenhouse gases released into Earth’s atmosphere reached new record high concentrations in 2019. The annual global average carbon dioxide concentration at Earth’s surface was 409.8 ± 0.1 ppm, an increase of 2.5 ± 0.1 ppm over 2018, and the highest in the modern instrumental record and in ice core records dating back 800 000 years. Greenhouse gases, along with several halogenated gases, have contributed to a 45% increase in net forcing compared to 1990. Carbon dioxide is responsible for nearly two-thirds of this increase. A weak El Niño early in the year transitioned to ENSO-neutral conditions by mid-year, yet the annual global surface temperature across land and ocean surfaces was still among the three highest on record. July became the hottest month in records dating to the mid- to late-1800s. Each decade since 1980 is warmer than its preceding decade, with 2010–19 being around 0.2°C warmer than 2000–09. In 2019, there were a record high number of extreme warm days (temperatures above the 90th percentile) over global land surfaces. There were also a low number of extreme cool days (temperatures below the 10th percentile) compared to the last 70 years, but there were more cool days compared to the average of just the past decade. A new indicator introduced this year to the report—marine heat waves—indicates that the number of strong marine heatwaves surpassed the number of more moderate marine heat waves for the sixth consecutive year. Lake temperatures increased on average across the globe in 2019; observed Northern Hemisphere lakes were covered in ice seven days fewer than the 1981–2010 average, accord- ing to phenological records. Over land, the growing season was an average of eight days longer than the 2000–10 average in the Northern Hemisphere. In colder regions, alpine glaciers around the world continued to lose mass for the 32nd consecutive year, while record high permafrost temperatures were observed at many observing sites across the high northern latitudes. The complete report can be found here: https://www.ametsoc.org/ams/index.cfm/publications/bulletin-of-the-american-meteorological-society-bams/state-of-the-climate/

Climate Proxies: Some resources: Introduction to Climate Science: Paleoclimate: https://open.oregonstate.education/climatechange/chapter/paleoclimate/ What is Paleoclimatology? https://www.ncei.noaa.gov/news/what-is-paleoclimatology Data: Paleoclimatology data: https://www.ncdc.noaa.gov/data-access/paleoclimatology-data

Abrupt as in taking place in a matter of decades rather than the far longer geological timeframes such changes have typical (not always) occurred. Actually, I probably should have used a somewhat different term, as abrupt can infer an unexpected development when the warming is consistent with the latest understanding of climate change. Also, there’s no need to dismiss the work of paleoclimatologists who have pieced together climate records from various proxies. The proxies offer a reasonably consistent picture. They provide a lot of insight. The alternative is to pretend that what wasn’t recorded is unknown and unknowable. That’s not a scientific approach.

No climate scientist has published a paper that argues that the climate was "in almost complete stasis" since 1000 CE. Climate has always been dynamic due to changes in natural forcings, not to mention internal variability. There have been periods where it has been relatively more stable than at other periods. The big issue concerns the abrupt and sharp warming that commenced since the mid-20th century, predominantly on account of anthropogenic greenhouse gas emissions. That warming has occurred despite little change in solar irradiance and a long-term decline in summer solar insolation in the Arctic. The change in the atmospheric concentration of CO2 and the warming that has occurred in mere decades is remarkable, as such changes have typically (not always) occurred over geological timeframes, not decades.

Phoenix recorded its hottest summer (June 1-August 31) on record. Anthropogentic climate change has been driving an observed global warming. Within that global climate context, Phoenix has experienced both a warming of its summers and a lengthening of its summer-like temperatures. If one looks back at the climate model projections for the RCP 4.5 scenario, one finds that the climate model projections run in 2005 were very accurate in depicting what the summer 2011-2020 period would be like. Looking ahead, the summer 2021-2030 period will likely be even warmer under the RCP 4.5 scenario. Phoenix: Summer 2011-20 High Temperatures and Projected 2021-30 High Temperatures:

Morning thoughts... Today will be partly sunny and warm. The temperature will likely top out mainly in the upper 70s with a few lower 80s across the region. Likely high temperatures around the region include: New York City (Central Park): 78° Newark: 80° Philadelphia: 78° The temperature will likely remain above normal through the remainder of the month. Yesterday was Las Vegas' 157th consecutive day with no measurable precipitation. That is the longest such stretch on record for that city.

Those claims are aimed at dismissing climate scientists to circumvent the absence of scientific evidence to dismiss AGW. While we’re discussing independence or perceived independence of researchers, it should be noted that Lindzen cited above had been receiving funding from coal interests (Peabody Energy). https://www.theguardian.com/environment/2016/jun/13/peabody-energy-coal-mining-climate-change-denial-funding

A review of the scientific literature on climate change and wildfires: https://news.sciencebrief.org/wildfires-sep2020-update/

New Record Low Northern Hemisphere Temperature: From the World Meteorological Organization: WMO has recognized a temperature of -69.6°C (-93.3°F) at an automatic weather station in Greenland on 22 December 1991 as the lowest ever recorded in the Northern Hemisphere. The temperature record was uncovered after nearly 30 years by “climate detectives” with the WMO Archive of Weather and Climate Extremes. It eclipses the value of -67.8°C recorded at the Russian sites of Verkhoyanksk (February 1892) and Oimekon (January 1933). The world’s coldest temperature record, of -89.2°C (-128.6°F) on 21 July 1983, is held by the high-altitude Vostok weather station in Antarctica. https://wmo.asu.edu/new-coldest-northern-hemispheric-temperature The related paper: https://rmets.onlinelibrary.wiley.com/doi/10.1002/qj.3901

CNN reported: California's Creek Fire is not only the largest single wildfire in the state known for huge and destructive blazes, it spawned two rare firenados a day after the fire started earlier this month. One firenado -- short for fire tornado -- was rated an EF-2, with winds up to 125 miles per hour. The other had winds of up to 100 miles per hour and was rated an EF-1. They wreaked havoc across the rugged area, the result of "unprecedented fire behavior," government forecasters said Thursday. https://www.cnn.com/2020/09/24/us/california-fire-tornado-creek-fire/index.html

As the issue about climate models has arisen on numerous occasions, here’s a good introduction from University of Arizona paleoclimatologist Jessica Tierney featuring NASA Goddard Institute for Space Studies Director Gavin Schmidt: In terms of model performance, here’s a recent paper that evaluates the performance of climate models: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085378

Temperatures rose in the 70s across the region today. Tomorrow will likely be somewhat warmer with more sunshine than today. In the Rockies, Denver reached 91° today. That surpassed the previous daily record of 89°, which was set in 1992. It was also Denver's 75th 90° or warmer day. The previous annual record was 73 days in 2012. Temperatures will likely remain at generally above normal levels for the remainder of September. A cool shot is possible to open October. Phoenix has an implied 91% probability of recording just its 13th September on record with a mean temperature of 90° or above. The most recent such occurrence was 2018 with a mean temperature of 91.8°. Phoenix will very likely record its hottest June-September period on record with a four-month mean temperature of 95.3°-95.5°. That would exceed the previous June-August record of 95.1°, which was set in 2013 and tied in 2015. The existing record is 93.9°, which was set in 2011. The ENSO Region 1+2 anomaly was -0.4°C and the Region 3.4 anomaly was -0.8°C for the week centered around September 16. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.93°C and the ENSO Region 3.4 anomaly has averaged -0.68°C. La Niña conditions have developed and will likely prevail through the remainder of autumn. The SOI was +14.26. Today, the preliminary Arctic Oscillation (AO) figure was +0.211. On September 23, the MJO was in Phase 5 at an amplitude of 1.368 (RMM). The September 22-adjusted amplitude was 1.168. Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. Based on sensitivity analysis applied to the latest guidance, there is an implied 70% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.4°.

Denver reached 90 degrees today for a record 75th time this year. The 91-degree temperature beat the previous daily record of 89 degrees, which was set in 1992.

A newly published paper revealed new evidence of a slowing of the Atlantic Meridional Overturning Circulation (AMOC) in response anthropogenic warming. The paper can found here.

The Arctic Dipole. https://www.amap.no/documents/doc/arctic-sea-ice-movement-pattern-and-arctic-rapid-change-pattern-arctic-dipole-anomaly/973

The authors of the MWP paper did not claim that the NAO was positive throughout the duration of the MWP. When one is dealing with centennial and sub-centennial timeframes, as was the case in the paper, one is dealing with predominant tendencies over those timeframes. A positive or negative tendency does not preclude even significant variability over much shorter timeframes. Weather is day-to-day; climate is longer-term. The authors found that the western North Atlantic region was generally cold during the MWP unlike the eastern North Atlantic region. Moreover, their study of the glacier record in the Baffin Bay region on which they based their conclusion is supported by additional proxy data. They explained: Overall, beyond the high-frequency complexity, we interpret these independent proxy records to support our glacier signal, indicating regional cool conditions through the MWP, perhaps interrupted by brief warming episodes. Our glacier record does not rule out periods of decadal warming between ~975 and 1275 CE, but the down-valley persistence of glaciers through this interval indicates that any warming was not of sufficient magnitude or duration to have driven glaciers significantly up-valley. In contrast to proxy records from the western North Atlantic region, records from the eastern North Atlantic region generally support warm conditions during the MWP. Historical observations and paleo-data indicate that sea ice off the Iceland coast was not common during the MWP, and an SST reconstruction off northern Iceland depicts a sharp rise in temperatures beginning ~1000 through ~1350 CE... The authors attribute the temperature anomalies to a persistent NAO+ state. This is a persistent tendency over the timeframe they covered. For example, let's say I was writing a paper on temperatures in the CONUS during the January 2012-2020 period. Among other variables, I could argue that a persistent NAO+ was responsible for the outcome. January 2012-2020: The argument against it would be, 'You can't maintain anomalies for such a period in either direction." But that would never have been my suggestion. If one went to the daily NAO data for the period in question, one would find: % days -1.000 or below: 1% % days negative: 24% % days positive: 76% % days +1.000 or above: 20% Each of the January cases during the period had a positive NAO value. The overall average daily value was just above +0.400. Now, if one steps back from this example and substitutes the MWP for the January 2012-2020 period and, let's say, year-to-year variability for daily variability in the NAO, one can still wind up with a skewed tendency for positive values over the timeframe considered, even as annual values would be both negative or positive. Finally, Andrew Dessler was not an author of the MWP paper. His background is in chemistry and physics. The climate system is comprised not just of the atmosphere, but also the hydrosphere, biosphere, and cryosphere. There is no compelling reason that Dr. Dessler is somehow unqualified for climate science. Also, do you have any papers that refute Dr. Dessler's work? Thanks.

For purposes of further comparison, below are RCP 4.5 projections (run in 2005) and the actual outcomes for Denver’s June-August high temperatures: 2016: Projection: 88.0 (Range: 83.7-92.3); Actual: 87.9 2017: Projection: 88.1 (Range: 83.7-92.4); Actual: 87.6 2018: Projection: 88.2 (Range: 83.8-92.5); Actual: 88.6 2019: Projection: 88.3 (Range: 83.9-92.6); Actual: 87.3 2020: Projection: 88.4 (Range: 83.9-92.7); Actual: 91.2 Five-Year Averages: RCP 4.5 Projection: 88.2 2016-2020 Average: 88.5

Greenhouse gases have played the dominant role in driving the observed warming, particularly since the late 20th century. They have not produced all the warming since the mid-20th century. Recent literature has suggested that the Medieval Warm Period was regional, not global in nature. The western Atlantic region was cold. The eastern Atlantic region was warm. The NAO has been suggested as a plausible explanation for the regional temperature variation during the MWP. https://advances.sciencemag.org/content/1/11/e1500806 Also, climate models should not be viewed as serving the same function as weather models. They are not intended to make day-to-day forecasts. They should not be viewed in such a context. Some of the major uncertainties that constrain weather model forecasts are largely irrelevant at the longer timescales used by the climate models. Their forecasts are of a more general nature over longer periods of time. Globally, they have been skillful in projecting the warming that has occurred. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085378 They have even done a reasonable job in projecting seasonal temperatures at a regional scale. As Phoenix was had a record-breaking summer, let's take a look at the last 5 summers as an example (bearing in mind that one should not use the climate models to make year-to-year forecasts, which are subject to a lot of internal variability). Below are RCP 4.5 projections (run in 2005) and the actual outcomes for Phoenix's June-August high temperatures: 2016: Projection: 106.3 (Range: 103.5-108.9); Actual: 106.2 2017: Projection: 106.4 (Range: 103.6-109.0); Actual: 106.5 2018: Projection: 106.4 (Range: 103.6-109.1); Actual: 106.0 2019: Projection: 106.5 (Range: 103.7-109.2); Actual: 106.8 2020: Projection: 106.6 (Range: 103.7-109.2); Actual: 108.6 Five-Year Averages: RCP 4.5 Projection: 106.4 2016-2020 Average: 106.8 Despite the extreme outcome of 2020--a glimpse of summers to come by 2050 according to the projections--the idea of summer high temperatures over a 5-year period, shorter than the decade-scale that is even more meaningful when dealing with climate projections, was very good.

Morning thoughts... Today will be variably cloudy and warm. The temperature will likely top out mainly in the upper 70s and lower 80s across the region. Likely high temperatures around the region include: New York City (Central Park): 78° Newark: 80° Philadelphia: 79° The temperature will likely remain above normal through the remainder of this week. Denver could make a run at 90° today. 2020 has already seen a record 74 such days there.

The 0.3 to 0.7C increase is the IPCC projection, not Curry’s. The idea that the “pause” or “hiatus” would continue into the 2030s appears to be on track to be wrong. In 2013, when the paper was published, the global temperature anomaly was +0.68C (GISS). The 2009-13 range was +0.61C to +0.72C. In 2019, the anomaly was +0.98C (2020 will finish in that vicinity). The 5-year range was +0.85C to +1.02C.