donsutherland1

From the NWS Phoenix forecast office:

Anthropogenic greenhouse gases are the dominant variable driving the changes.

The IOD state at this time of year doesn’t seem to have much influence. During the winter, and IOD- has often seen an increased tendency for the MJO to reside in the Maritime Continent phases (Phases 4 and 5).

Because the empirical evidence is strong. It assumes basic understanding that statistics measure things. Statistics are not abstractions unto themselves. The changes taking place are leading to warmer, drier conditions in general. The incidence of extreme heat, including this August’s record-breaking heat in parts of California and Arizona have increased the frequency of conditions that are conducive for wildfires.

You misunderstand the differences of climate (fixed point in time) and climate change (delta between two states of the climate) and the role that measurements play in providing insight into both. An analogy is useful: Average heart rate is a statistic. Average heart rate has no power over one’s health and has never caused one a heart attack or other serious heart issue. The underlying assumption, if one applies the implicit arguments concerning climate change to this measure, would be that whether one’s heart rate is rapidly slowing or becoming highly irregular would be irrelevant. In other words, there’s nothing to see. That would be dangerously naive. Large and dramatic changes could well indicate that a person is suffering a heart issue which, if not addressed, could pose a mortal threat. The same holds true for climate statistics. The change over time has meaning. And, because there is a relationship between many of the climate variables (higher temperatures-incidence of extreme heat, changes in global distribution of temperatures and the jet stream, greater warmth-greater capacity of the atmosphere to hold moisture, etc.) the overall changes taking place pose risks ranging from heat waves, drought, rising sea levels, etc. None of these changes are trivial.

If the idea that Phoenix’s climate will resemble that of Baghdad is reasonably accurate, then there could be some nights with lows at or above 100 (Phoenix’s lows are higher than those in Baghdad) and highs in the lower and middle 120s during periods of extreme heat.

Phoenix concluded, by far, its hottest summer on record. During June-August 2020, Phoenix had a mean temperature of 96.7°. That smashed the old record of 95.1°, which was set in 2013 and tied in 2015. Table 1: Summer 2020 Average Temperatures Since 2009, every summer has ranked among the 20 warmest summers on record. In addition, 2015, 2016, 2019 and 2020 have ranked among the 10 warmest summers. Table 2: 20 Warmest Summers Monthly Mean Temperatures: June: 92.0° (21st warmest June on record) July: 98.9° (warmest July on record; old record: 98.3°, 2009) August: 99.1° (warmest August on record; old record: 98.3°, 2011) July 2020 set a new monthly mean temperature. August 2020 surpassed that record. Just 3 (15%) of the 20 warmest months were recorded prior to 2000. 17 (85%) of the warmest months occurred 2000 or later and 10 (50%) of the warmest months occurred 2010 or later. There were three cases where both July and August ranked among the 20 warmest months: 2007, 2019 and 2020. Table 3: 20 Warmest Months Table 4: Record High Minimum Temperatures Table 5: Record High Maximum Temperatures Select Monthly Heat Thresholds: Highs 110° or above: 22 days, August 2020 (old record: 19 days, July 2020; prior old record: 18 days, June 1974) Highs 115° or above: 7 days, August 2020 (tied record set in June 1974) Lows: 90° or above: 16 days, July 2020 (old record: 11 days, July 2006); August 2020 had 12 such days. Select Summer Heat Thresholds: Highs 110° or above: 48 days (old record: 31 days, 2007 and 2011) Highs 115° or above: 13 days (old record: 7 days, 1974) Lows: 90° or above: 28 days (old record: 15 days, 2003 and 2013) Climate Change: Anthropogenic climate change is driving a warming of Phoenix's summers. The warming has accelerated in recent decades. The observed global warming since the 1950s is unequivocal with anthropogenic greenhouse gas emissions being the dominant driver of that warming (IPCC Climate Change Synthesis Report 2014). The warming is a global phenomenon with 98% of the world having experienced its warmest 51 years during the current 2,000 years (Neukom, et al. 2019). Recent research suggests that Phoenix's climate will resemble that of Baghdad by 2050 (Bastin, et al. 2019). During the summer, Baghdad typically receives no rainfall. Baghdad's average high temperatures (Weather Atlas 2002-2020) during the summer months are: June: 105.8° July: 111.2° August: 109.4° Summer Average High Temperature: 108.8° Until summer 2020, the highest mean summer maximum temperature was 107.0°, which was set in 1978 and tied in 1989. The highest monthly summer maximum temperature was 109.8°, which was set in July 1989 and tied in July 2020. August 2020 surpassed that record with an average high temperature of 110.7°. As recently as 2000, Phoenix's average low temperature during the summer was 79.8°. Since 1999, Phoenix has had no summer with an average low temperature below 80.0°. Prior to 2020, the highest average monthly minimum temperature was 87.5°, which was set in August 2011. July 2020 had an average minimum temperature of 88.0°. Based on the above research findings, summer 2020 provides a glimpse of what a typical Phoenix summer will be like by 2050. Table 6: Average Summer Temperatures (30-Year Moving Average) Climate change is also resulting in an increase in the frequency of days on which the low temperature stays at or above 90° and the high temperature reaches 100° or above, 110° or above, and 115° or above. Table 7: Average Annual Days at Set Thresholds (30-Year Moving Average) According to the Fourth National Climate Assessment, Phoenix saw 60 to nearly 100 100° days per year at the 5th and 95th percentiles. Under the RCP 4.5 scenario, those figures are projected to increase to 110-141 days per year during the 2070-2099 period. During the 1950-1999 period, 9 (18%) of years saw the number of 100° days fall within the projected RCP 4.5 interval (U.S. Global Change Research Program, 2017). From 2000-2019, 11 (55%) of years fell within that interval. 2020 is all but certain to become the 12th case since 2000 to meet that higher interval. Moreover, through August 31, the 30-year moving average is just above 110 days per year. During the summer, 48 days saw high temperatures 110° or above. The previous summer record was 31 days, which was set in 2007 and tied in 2011. During 2020, there have been 50 such days vs. the prior record of 33 days, which was set in 2011. There were also 28 days on which the minimum temperature was 90° or above, which eclipsed the previous record of 15, which was set in 2003 and tied in 2013. In addition, the number of very hot (high temperature of 110° or above) and super hot (high temperature of 115° or above) days has been increasing as a share of the increasing number of 100° days. For the 30-year period ending in 1980, 12.6% of 100° days had high temperatures of 110° or above and 1.0% saw temperatures reach 115° or above. For the 30-year period ending in 2000, those figures increased to 15.7% and 1.7% respectively. For the period ending in 2020 (through August 31), those figures increased further to 18.8% and 2.0% respectively. Overall, the frequency and intensity of compound summertime hot extremes (events that combine daytime and nighttime heat where such temperatures are above their 90th percentile for their calendar) has been increasing especially in geographic locations that include the U.S. Southwest (Wang 2020). The increase in forcing associated with anthropogenic greenhouse gases is the dominant driver of this outcome. (Wang 2020). During summer 2020, 15 record high minimum temperatures were tied or broken in Phoenix and 14 record high maximum temperatures were tied or broken. On 7 days, both record high minimum and maximum temperatures were tied or broken. Summary: Summer 2020 saw Phoenix record its highest summer temperature on record. It also saw Phoenix experience its two hottest months on record. In addition, Phoenix easily surpassed records for the most days on which the temperature reached 110° or above and on which minimum temperature was 90° or higher. Anthropogenic climate change, which has turned hot patterns hotter and increased pattern persistence, is largely responsible for this exceptional warmth. Based on the latest research, the extreme heat of summer 2020 will likely become the "new normal" by 2050. Updates: September 1-7: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5650331 Summer High Temperatures: Climate Model Projections and Actual Outcomes: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5661632 Phoenix Records a 90° Mean Temperature for September: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5664607 Phoenix Experiences its Hottest Week in October: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5668129 Phoenix Sets New Annual Record for 100° Days: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5672012 A Very Warm October Concludes in Phoenix: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5684211 Phoenix Experiences its Warmest 5-Day November Period on Record: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5687553 Phoenix Experiences Latest 90° Days on Record: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5698629

A healthier diet and other lifestyle changes, independent of anything to do with climate change, would likely reduce comorbidities among the American population, expanding with life spans and the quality of life.

September Preview: In the New York City area, September has increasingly become an extension of summer. Prior to 2000, a monthly mean temperature of 70° or above was relatively uncommon. Prior to 1950, Central Park saw such warmth about once every 5.4 years. From 1950-1999 (during which New York City has had a mature urban footprint), such warmth was recorded approximately once every 4.5 years. Since 2000, 70° Septembers have occurred about once every 2.0 years. There have been 10 such Septembers during the 2000-2019 period, which is just below the figure of 11 recorded during 1950-1999. Since 2010, New York City has had 7 cases where September had a mean temperature of 70° or above, including the last four years. During the last 30 years, September has had a mean temperature of 69.0°, which is the warmest 30-year period on record for September. During the last 10 years, September has had a mean temperature of 70.5°, which is the warmest 10-year period on record for that month. Records go back to 1869. The 1981-2010 normal temperature for September is 68.0°. New York City's 30-Year Moving Averages for September: 30-Year Period ending: 1990: 68.1° 2000: 68.1° 2010: 68.4° 2019: 69.0° September 2020: 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°. Overall, the evolution of ENSO, along with the observed ongoing monthly warming (1.6°/decade in NYC and 1.5°/decade in the Northeast Region during September 1990-2019), favors a warmer than normal September. The first half of September will likely see a deep trough located over the Great Lakes to Central Canada. However, the Western Atlantic Ridge could blunt the amount of cool air that reaches the New York City area. Afterward, that trough could dissipate. Overall, September will likely wind up with a mean temperature near 70° or about 2° above normal in New York City.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 1.8 2.0 1.7 0.0 1.0 0.3 0.2 2.7 3.2

Arctic sea ice extent fell to 3.995 million square kilometers on JAXA. That makes 2020 the second consecutive year that will have a minimum extent below 4.000 million square kilometers and the third such year on record.

I suspect the problem with the “Green New Deal” has less to do with its climate provisions than with the non-climate provisions. Hopefully, sooner rather than later, science will take precedence over other interests when it comes to addressing the challenge of climate change.

It is. The IPCC is considering increasing the confidence figure for anthropogenic factors being the dominant cause of the ongoing warming to 99%-100% from 95%. The evidence is all but unequivocal now. I agree concerning future generations. That they will bear the highest costs from inaction, they will likely point to that inaction as being among the greatest failures in human history. They won’t be wrong. Moreover, I suspect that when Generation Z attains political leadership, they will make drastic changes (e.g., net carbon neutrality in a decade or less) to address the problem if little has been done. Inaction is squandering the time available for a transition.

This year one is seeing an IOD- pattern. Last year one saw among the strongest IOD+ patterns.

No one has made the misleading argument that 'statistics cause or drive weather.' They are measures. Nothing more. Statistics measure the state of weather and, over longer timeframes, the state of the climate. Climate change in the conventional use of the term concerns the changes taking place among, other things, measures of temperature, precipitation, etc. The data is now almost unequivocal that the world has been warming. The scientific research also overwhelmingly attributes that warming to anthropogenic factors. The literature reveals that the increased tendency for hot and dry conditions is creating more favorable conditions for wildfires. The massive wildfires witnessed in recent years in Australia, California, parts of Europe, and Siberia are not random occurrences. The climate research has already accurately forecast an increased incidence of such events.

Unfortunately, the added heat from the growing greenhouse gas forcing is triggering more extremes. Balance is being sought in more damaging fashion.

Another relevant article on the California fires and climate change: https://yaleclimateconnections.org/2020/08/climate-change-is-worsening-californias-hellish-wildfires/

Almost certainly, climate change has driven the increased incidence of wildfires on a global basis. Brazil’s deliberate policy of land clearing in and around the Amazon has amplified the situation there. In fact, as the Amazon is reduced in size, that development will feedback in greater drying due to the loss of rainforest and increased fire risks.

There's a growing body of literature linking climate change to a slowing of the jet stream. The end result is "stuck patterns." Alaska's record warm summer last year, Siberia's record warmth earlier this year, and Phoenix's record-setting summer this year are some recent examples resulting from a greater persistence in prevailing patterns.

This PBS Newshour interview was conducted in 2018 but is as timely now as it was then. Since then, Australia recorded its worst fire season on record. More big wildfires are currently burning in California. https://www.pbs.org/newshour/show/climate-change-is-making-wildfires-more-extreme-heres-how And an animated satellite photo from the August 2020 fires in California:

Unfortunately, based on 2010-19 melt rates, it is very likely that 2020 will finish solidly with the second lowest minimum extent on record. It will also be the second consecutive year with a minimum extent below 4 million square kilometers and third such year on record.

Yes. Central Park had an 80.0 mean temperature.

Today, Arctic sea ice extent was 5,994,562 square kilometers (JAXA). That is the earliest date on record on which Arctic sea ice extent fell below 6 million square kilometers. The previous record was set just last year on July 30, with a figure of 5,997,752 square kilometers.

Absolutely. Such costs will likely continue to rise, as sea-level rise flooding from melting ice in Greenland and Antarctica is continuing to increase. The NOAA’s most recent report: https://tidesandcurrents.noaa.gov/publications/Techrpt_092_2019_State_of_US_High_Tide_Flooding_with_a_2020_Outlook_30June2020.pdf

Arctic sea ice extent fell to 6.996 million square kilometers (JAXA) today. The previous earliest figure below 7 million square kilometers was July 19, 2011 when extent was 6.995 million square kilometers.