Climate Change Blogs

Absurd January Warmth in Arctic Brings Record-Low Sea Ice Extent

Published: 4 février 2016
This winter’s freezing season in the Arctic is falling short. The extent of Arctic sea ice this week is hovering near record-low values for early February, based on observations that extend back to the start of satellite monitoring in 1979. Data from the National Snow and Ice Data Center (NSIDC) shows that last month had the lowest overall Arctic sea ice extent of any January in the satellite record (Figure 1). As detailed in an NSIDC report on Thursday, the total extent of 13.53 million square kilometers (5.2 million square miles) was 1.04 million sq km below the 1981-2010 average and 90,000 sq km below the record from January 2011.



Figure 1. Departures from average in Arctic sea ice extent for January, 1979-2016. Image credit: NSIDC.


Figure 2. Sea ice extent for January 2016 (white), compared to the median January location of the ice edge for the period since 1979 (magenta line). The largest areas of open water where ice is usually present are in the Barents Sea, north of Scandinavia. Image credit: NSIDC.

Only a few weeks are left before the return of polar sunshine puts an end to the freeze-up that typically starts in September and peaks in late February or March. Last year’s maximum extent occurred quite early--on February 25--and it was the lowest in the satellite record, at 14.54 million square kilometers. This year appears to have a reasonable shot at breaking that record.

The not-so-frozen North
Hand in hand with the skimpy ice cover, temperatures across the Arctic have been extraordinarily warm for midwinter. Just before New Year’s, a slug of mild air pushed temperatures above freezing to within 200 miles of the North Pole. That warm pulse quickly dissipated, but it was followed by a series of intense North Atlantic cyclones that sent very mild air poleward, in tandem with a strongly negative Arctic Oscillation during the first three weeks of the month (see Figure 4).


Figure 3. Average air temperatures over the Arctic for January 2016 at the 925-mb level (about 2000 feet above the surface), expressed as departures from the long-term January average in degrees C. Image credit: NOAA Earth System Research Laboratory.


“January was absurdly warm in the Arctic,” said NSIDC director Mark Serreze. According to data from NOAA’s Earth Systems Research Laboratory, the average surface temperature in January between latitude 60°N and the North Pole was -18.2°C (-0.8°F), topping the previous record of -20.6°C (-5.1°F) set in January 2005. Just above the surface (925 mb), the average January temperature of -14.2°C (5.9°F) was well above the previous record of -16.5°C (0.7°F), also set in 2005. The fact that average readings at this level are warmer than at the surface reflects the strong inversion typical of the lower Arctic atmosphere, especially in winter, as cold air hugs the surface and milder air flows just above it.


Figure 4. This cross section through the polar vortex (between latitudes 65°N and 90°N) shows how the height of pressure surfaces (shown in millibars/hPa on the left-hand axis) varied over time from October 2015 to early February 2016. Red values show where a given pressure surface was unusually high in the atmosphere, corresponding to warmer-than-average temperatures. The temperatures have been normalized so that the right-hand legend shows standard deviations from the mean. Image credit: NOAA Climate Prediction Center.

Anyone for bathing in the Barents?
Some of the most visible ice-extent deficits right now are in the Barents Sea, north of Scandinavia. Warm waters carried by the Atlantic Meridional Overturning Current (AMOC) can push all the way northeast into the Barents, making it one of the most variable of the seas that fringe the Arctic. Data from Crysophere Today (University of Illinois at Urbana-Champaign) show that sea ice now covers less than half the area across the Barents that it did a year ago at this time. The difference in area--roughly 350,000 square kilometers--is bigger than the state of New Mexico. (Note that sea ice area is a somewhat different index than sea ice extent, as explained by NSIDC.)

Near the northwest corner of the Barents Sea, temperatures in Svalbard, Norway--at 78°N, the northernmost civilian community on Earth--have been far above average for the entire last month. From January 5 to February 3, the average in Svalbard was -4.7°C (23.5°F), which is a full 19°F above the norm--remarkable for a 30-day period. The coldest reading of the whole period, -11.9°C, was still above the average January high of -13.0°C! Temperatures pushed above freezing on four days, reaching 4.5°C on January 24 (still not a monthly record, though). The WU forecast shows Svalbard remaining unusually mild for at least the next week, with lows at or above the average highs.


Figure 5. The area covered by sea ice in the Barents Sea as of February 4 was around 250,000 square kilometers (right side of black trace), less than half of the value a year ago (left side of black trace). The red trace shows departures from average for the time of year. Image credit: Cryosphere Today/University of Illinois at Urbana-Champaign.

The outlook for 2016
Most of the attention around Arctic sea ice has focused on the dramatic losses in summertime, especially over the past decade. The minimum yearly extent set new record lows in 2007 and again in 2012. Both of these minimums were followed by a year or two of quasi-recovery, but then the long-term trend toward lower summer minimums resumed.

Could 2016 set another new record minimum? It’s far too soon to make any confident predictions. A record-low maximum could give the ice a head start on 2016 melting, but the ultimate outcome will depend mainly on weather patterns still to come, especially in early summer. Warm southerly winds and clear, sunny skies during June and July can make a huge difference in paving the way for a record minimum in September.


Figure 6. The years 2012 (green dashed line) and 2015 (blue line) show how the state of sea ice in late winter and spring doesn’t necessarily correspond to its minimum in September. Sea ice extent in March 2012 was near its long-term average in April, yet it was at a record low in September. Late winter ice was much less extensive in 2015, but that year’s minimum was still considerably higher than in 2012. The extent for 2016 is shown in the red line at far left. Image credit: NSIDC.


Those on the front lines of experimental sea ice prediction stress the role of weather conditions in modulating how any one season will fare. In a 2015 review paper for EOS, Julienne Stroeve (NSDIC) and colleagues from the Sea Ice Prediction Network took a look at what recent efforts have accomplished and what may be possible down the line. Since 2008, the network has issued monthly compilations of sea ice forecasts (available online) updated through the summer, created by more than a dozen participants using a variety of methods. The average of these predictions tends to do somewhat better than any one approach, but even that skill is still limited, especially more than a month or two in advance of the September minimum.

“Because the atmosphere is mostly unpredictable beyond 1 or 2 weeks, the sea ice forecasts initialized in late spring may not be able to accurately predict sea ice features that develop as a result of extreme summer atmospheric conditions,” said the EOS paper.

Idealized experiments suggest that the state of Arctic sea ice might be predictable with some skill as far as two years in advance. To reach this theoretical goal, we would need major advances in both Arctic observations and modeling. There’s another catch: climate change itself may make the task harder. “Interannual variability of summer sea ice extent will likely increase in coming decades,” noted Stroeve and colleagues, “and some scientists suggest that this might lead to a reduction in predictability.”

We’ll be back with a new post on Friday.

Bob Henson

Yearly, Monthly Heat Records Dissolve In 2015's Global Onslaught

Published: 21 janvier 2016
The year 2015 ended in spectacular fashion, winding up as the warmest year in more than a century of recordkeeping--and it’s wasn’t even close to a photo finish. NASA and NOAA held a joint press conference on Wednesday to release their global climate assessments for the year. It had become obvious in recent weeks that 2015 was heading toward a new record high, but the final numbers were still startling. NOAA calculated that the average global temperature across both land and ocean surfaces for 2015 was 0.90°C (1.62°F) above the 20th-century average of 13.9°C (57.0°F). This makes 2015 the warmest calendar year, as well as the warmest of any 12-month period, in global temperature data going back to 1880. Using a slightly different technique, NASA confirmed that 2015 was the warmest year in this 136-year period.

The margin of 2015’s victory is itself noteworthy. NOAA calculated that 2015 beat the previous record warmth of 2014 by 0.16°C (0.29°F), which is the largest such margin for any year. NASA came up with a slightly smaller value--0.13°C (0.23°F)--which tied with 1998’s margin of victory.

Last year was the third-warmest on record for satellite-based estimates of temperature through the lowest five miles of the atmosphere, as calculated by the University of Alabama in Huntsville (UAH). Record warmth was recorded for autumn (September-November) as well as for December. Because these are indirect, large-scale estimates of temperature well above ground level, derived from satellite data, they need not correspond to trends in direct ground-based measurements of surface temperature.


Figure 1. Yearly global temperature (as expressed against the 20th-century average), 1880 - 2015. Shaded red bars indicate the average for each decade. Despite a relatively flat temperature trend in the first decade of the 2000s, global warming didn’t “stop” then. Each decade since the 1960s has been warmer than the prior one. Image credit: NASA/NOAA.



Figure 2. Departure of temperature from average for 2015, the warmest year for the globe since record keeping began in 1880. Image credit: National Centers for Environmental Information (NCEI) .

The role of El Niño
We can give El Niño credit (or blame) for part of this year’s record-smashing global temperature, but the shadow of longer-term warming due to human influence is inescapable. El Niño events tend to increase heat transfer from the ocean to atmosphere by spreading warm water across a broad stretch of the tropical Pacific, so as our climate warms, we can expect the biggest record-year spikes to occur during El Niño (as evident in Figure 2, below). That said, the huge margin of 2015’s record is comparable to the typical amount of global-scale warmth produced by a strong El Niño: several tenths of a degree Celsius. This means that 2015 may well have set a record even if El Niño were absent.

“2015 was remarkable even in the context of the ongoing El Niño,” said NASA/GISS director Gavin Schmidt. “Last year’s temperatures had an assist from El Niño, but it is the cumulative effect of the long-term trend that has resulted in the record warming that we are seeing.”


Figure 3. Departures from average in global monthly temperature from 1980 to 2015, with colors showing whether each month was characterized by El Niño (red), La Niña (blue), or neutral conditions. Image credit: NASA/NOAA.

What next?
The second year of a major El Niño tends to warm the global atmosphere even more than the first, as the atmosphere gradually adjusts to the ocean-surface warming. This means that 2016 has a very good shot at breaking the global temperature record that was just set by 2015, which in turn beat out 2014. Since records began in 1880, there have never been three consecutive record-warm years--another piece of evidence that long-term climate change is underpinning our current string of warmth. It would be exceedingly unlikely for El Niño to extend into 2017, so we might expect that year to break the string, but barring a huge volcanic eruption, the decade of the 2010s has an excellent chance of ending up warmer than the 2000s (see shaded bars in Figure 1).

The UK Met Office will soon be releasing its annual forecast of global temperature for the next decade (here’s the forecast issued in January 2015). As we discussed early last year, the now-positive state of the Pacific Decadal Oscillation suggests that we may have embarked on a decade or two of more-frequent El Niño events and accelerated atmospheric warming, similar to what occurred in the 1980s and 1990s. The PDO helps explain a good bit of the multidecadal variation in global temperature, including the slowdown in atmospheric warming evident in the 2000s and early 2010s. During these slowdowns, Earth’s oceans are taking up a larger fraction of the heat being trapped by human-produced greenhouse gases; during the speedups, the oceans are returning some of that heat to the surface. All the while, ever-increasing amounts of human-produced greenhouse gases are pushing up both the peaks and valleys of global temperature.

Earth's warmest December on record
In a fitting capstone to a sizzling year, December 2015 was the warmest calendar month in Earth’s 136-year temperature record, according to the NOAA/NCEI monthly recap released on Wednesday. December 2015 was the eighth consecutive month that a monthly high temperature record was set in NOAA's database. NASA also rated December 2015 as the single warmest calendar month in its database.

Figure 4. Departure of temperature from average for December 2015, the warmest December for the globe since record keeping began in 1880. Record warmth was observed over vast swaths of the globe, including far eastern North America, northern South America, southern Africa, and central and northern Europe, as well as most of the equatorial Indian Ocean and western North Atlantic. Image credit: National Centers for Environmental Information (NCEI) .

Arctic sea ice comes in at 4th lowest December extent on record
Arctic sea ice extent during December 2015 was the 4th lowest in the 36-year satellite record, according to the National Snow and Ice Data Center (NSIDC). An usual surge of warm air during the last week of December that brought temperatures above freezing close to the North Pole, and brought sea ice formation to a virtual halt. Arctic sea ice was close to a record minimum (for that time of year) going into 2016, possibly due to this warm surge.

Notable global heat and cold marks set for December 2015
Hottest temperature in the Northern Hemisphere: 40.6°C (105.1°F) at Armero, Columbia on December 26 and 31, and also at Guaymaral, Colombia on December 31.
Coldest temperature in the Northern Hemisphere: -63.8°C (-82.8°F) at Geo Summit, Greenland, December 16.
Hottest temperature in the Southern Hemisphere: 47.2°C (117.0°F) at Port Augusta, Australia, December 19.
Coldest temperature in the Southern Hemisphere: -43.1°C (-45.6°F) at Dome Fuji, Antarctica, December 1, and at Pole of Inaccessibility, Antarctica, December 2.

Major stations that set (not tied) new all-time heat or cold records (for any month) in December 2015
Queenstown (South Africa) max. 40.4°C  1 December
Estcourt (South Africa) max. 40.4°C 1 December
Belem (Brazil) max. 38.5°C 1 December
Caxias (Brazil) max. 42.7°C 2 December
Vryburg  (South Africa) max. 42.3°C 6 December
Van Zylsrus (South Africa) max. 43.8°C 6 December
Kuruman  (South Africa) max. 40.8°C 7 December
Frankfort  (South Africa) max. 38.1°C 7 December
Pretoria  (South Africa) max. 41.0°C 7 December
Ottosdal  (South Africa) max. 42.0°C 7 December
Rustenburg (South Africa) max. 39.4°C 7 December
Bethlehem (South Africa) max. 35.6°C 7 December (revised to 36.2°C on 24 December)
Cooma (Australia) max. 39.5°C 20 December
Ladysmith (South Africa) max. 41.5°C 24 December
Richard Bay (South Africa) max. 42.7°C 24 December
Cedara (South Africa) max. 40.4°C 24 December
Pietermaritzburg (South Africa) max. 42.1°C 24 December
Tigerhoek (South Africa) max. 43.2°C 30 December
Robertson (South Africa) max. 44.8°C 30 December

Kudos go to Maximiliano Herrera for supplying the data for the "Notable global heat and cold marks set for December 2015" and "Major stations that set (not tied) new all-time heat or cold records in December 2015" sections of the post.

Coming up: full coverage of the big mid-Atlantic snowstorm
We’ll have a full update Thursday afternoon on the mammoth winter storm that will be developing from the central Appalachians onward to the East Coast over the next several days. Computer models remain insistent that snow amounts of 15-25” are quite possible over large parts of Virginia, West Virginia, Maryland, and the District of Columbia. High-impact snows may extend further north, but the uncertainty there is greater, and the amounts should drop off rapidly toward the north edge of the storm (see embedded tweet below for one forecaster’s unofficial take). If you are in the targeted areas, now is the time to make any needed preparations. To find out the odds that a given amount of snow will fall in your area, check out the innovative probabilistic maps being generated by the NWS offices serving the Baltimore-Washington and New York City areas. We’ll be covering the storm with a WU liveblog on Friday and Saturday; watch for details.

Jeff Masters and Bob Henson


Warm, Wet Year for U.S.; Record Heat in South Africa; Tropical Storm Pali Intensifies

Published: 8 janvier 2016
Many Americans were throwing on T-shirts or rain gear instead of heavy coats last month, in what proved to be the nation’s mildest and wettest December in more than a century of record-keeping. On Thursday, NOAA’s National Centers for Environmental Information (NCEI) released initial data on December and for the year 2015. (A full report will be issued on January 13). As a whole, 2015 came in as the second warmest and second wettest year on record for the contiguous U.S.

It’s hard to overstate the striking character of December’s mildness. Millions of people along the Eastern Seaboard experienced it first hand, as all of the big cities (and many smaller ones) from Washington, D.C., to Portland, Maine, smashed their previous records for December warmth. New York City’s Central Park went through the entire month of December without dipping down to freezing, whereas all prior Decembers back to 1871 had reached 32°F at least six times. As shown in Figure 1, each state east of the Mississippi--plus Minnesota, Iowa, and Missouri--saw its warmest December on record, and even the coolest states were close to their long-term December average. All told, close to 12,000 daily records (warm highs and warm lows) were set across the nation in December, as noted by weather.com. There was plenty of moisture to be had as well: 40 states came in above average on precipitation, with Iowa and Wisconsin getting their wettest December on record and Minnesota, Missouri and Illinois coming in at second-wettest. These rains contributed to the exceptional flood crest now moving along the lower Mississippi River.


Figure 1. Temperature and precipitation rankings by state for December 2015. Higher numbers indicate warmer and wetter conditions. States labeled 121 (dark red and dark green) experienced the warmest or wettest Decembers in 121 years of national recordkeeping. Image credit: NOAA/NCEI.


For the year as a whole, the warmth and moisture were widely distributed across the contiguous U.S. There were more than twice as many daily record highs as record lows for the year, but as noted by Climate Central, a brutally cold February over the eastern U.S. was the main factor keeping 2015 from being the nation’s warmest year. The northwest and southeast corners of the 48 states, Washington and Florida, both had their warmest year on record, as did Oregon and Montana. All 48 contiguous states saw at least a top-25 warmest year. Only five were notably drier than average in 2015--California, Montana, Connecticut, Rhode Island, and Massachusetts--while many central states had a top-10 wettest year, with Texas and Oklahoma notching their wettest on record. (During the first week of 2016, moisture has also returned to California in a big way, thanks to a parade of soggy Pacific storm systems; more on that in a future post.)


Figure 2. Temperature and precipitation rankings by state, as in Figure 1, but for the entire year of 2015 (January – December). Higher numbers indicate warmer and wetter conditions. States labeled 121 (dark red and dark green) experienced the warmest or wettest year in 121 years of national recordkeeping. Image credit: NOAA/NCEI.


How did the U.S. stay so mild and moist at the same time?
The combination of unusual warmth and unusual moisture is a standout in itself. Heavy, persistent precipitation often means lots of sun-blocking clouds that cut down on heating. Very warm months are typically the driest ones. That was the case in June 1933 and May 1934, two Dust Bowl months that still reign as the warmest and driest May and June in U.S. history (thanks to Nick Wiltgen at weather.com for this find). What made the difference last month, and last year, was the record-warm sea surface temperatures over the tropical Pacific and Atlantic, a function of El Niño and other short-term oceanic patterns as well as long-term warming related to human-produced climate change. These warm SSTs allowed vast amounts of moisture to evaporate into air masses flowing toward the lower 48 states. In turn, this led to countless records for precipitable water (the amount of water vapor in the air above a given measuring site). Near the surface, the moisture helped to keep nighttime temperatures consistently high in many locations.

Here’s just one example: During the nine-day period from December 23 to 31, the lowest temperature observed in Key West, Florida, was 78°F. This happens to be the previous record-warm minimum for the entire month of December, going back to 1871! This is the first time I’ve heard of any U.S. location with more than a century of weather-observing history that managed to tie or set a monthly record on so many consecutive days. Key West’s daily lows were an astounding 79°F on December 25, 27, 28, 29, and 31. Finally, on January 3, the mercury dropped below 69°F, for the first time since April 1--making it the longest such streak at or above 69°F (277 days) in Key West history.


Figure 3. Average temperatures for the period September-December since 1895 for the contiguous U.S. This past Sep-Dec was more than 1°F warmer than the previous record-holder, 1998. Image credit: NOAA/NCEI.


The big wet
Two states saw their wettest months on record in May 2015: Texas (8.81”) and Oklahoma (14.40”). South Carolina didn’t manage that feat during its extreme October deluge, but the state did end up with its wettest autumn on record (23.62”, more than 5” above the previous record). Hand in hand with these large-scale dousings, there were some particularly hefty year-long accumulations at individual sites, including these wettest local years on record:

St. Louis, MO: 61.24” (old record 57.96” in 2008)
Fort Smith, AR: 73.93” (old record 71.81” in 1945)
Dallas-Fort Worth, TX: 61.61” (old record 53.54” in 1991)



Figure 4. A Japanese camellia (japonica) in bloom at Danville, Virginia, on December 25, 2015. Image credit: wunderphotographer WeatherWise.


A Christmas warm wave for the ages
December culminated in a memorable week-plus period of record warmth that swaddled most of the nation east of the Rockies. On Christmas Eve and Christmas Day, a total of 847 U.S. stations tied or broke record daily highs, according to preliminary data on NOAA’s U.S. Records website. Dozens of those previous marks were bested by at least 10°F. In Hanover, New Hampshire, it was 67°F on Christmas Day--a full 17°F warmer than any other Christmas in 122 years of recordkeeping. Just after noon on Christmas Eve, the heat index in Virginia Beach, VA, reached an absurdly unseasonable 86°F! Not to be outdone, the northwestern Alaska town of Kotzebue basked in the relative warmth of 37°F--tying its record monthly high--on the evening of December 30.

Chilly weather has returned to much of the central and eastern U.S. for early January. Although the cold is a bracing experience for those who got accustomed to extreme autumn mildness, it’s merely garden-variety chill by climatological standards. We are unlikely to see many record lows or record-cold highs in the foreseeable future, whereas a day of near-record warmth is once again possible in the mid-Atlantic and southern New England on Sunday. Still, one of the coldest pro football games in recent decades is on tap for Sunday, when the Minnesota Vikings will host the Seattle Seahawks in a wild-card playoff. Though probably well above record levels, temperatures at the 12:05 pm kickoff at the non-domed TCF Bank Stadium in Minneapolis are expected to be near or just below 0°F, with a wind chill as cold as –20°F possible. According to the Weather Channel’s Michael Butler, the Seahawks have never played in temperatures any colder than 16°F (Dec. 3, 2006, in Denver). The Vikings, who are temporarily based at TCF Bank Stadium while awaiting a new roofed stadium, have kicked off only once before in subzero weather: on Dec. 3, 1972, with a temperature of -2°F.

All-time record heat in southern Africa
A heat wave in the midst of an already scorching summer has baked southern Africa this week, producing the hottest readings ever observed in a number of locations. According to weather records researcher Maximiliano Herrera, Botswana set the world’s first all-time national high temperature of 2016 on Wednesday, January 6, then exceeded it on Thursday, January 7, as the city of Maun hit at least 43.8°C or 110.8°F (officially rounded upward to 44°C). Herrera, one of the world's top climatologists, maintains a comprehensive list of extreme temperature records for every nation in the world on his website, which lists dozens of all-time local record highs set since the first of this year across South Africa, Botswana, and Zimbabwe. South Africa’s capital city, Pretoria, soared to 42.7°C (108.9°F) on Thursday--the most recent in a string of several all-time record highs there over the last few weeks. In the nation’s largest city, Johannesburg, an all-time record of 36.5°C set only last November has been topped several times, most recently on Thursday with a high of 38.9°C (102.0°F). The heat across South Africa has also toppled many all-time world temperature records for any location at altitudes between 1000 and 1600 meters (3280 - 5250 feet), according to Herrera.

A severe multi-year drought in and near South Africa has drained reservoirs, devastated farming, and parched the landscape, allowing the summer sun to heat the land and air more efficiently (the same process that fostered record heat in California over the last several years). Making things worse, El Niño tends to produce drier-than-average conditions over southern Africa. Record-warm temperatures over the Indian Ocean are also playing a role, according to researchers. “The warming of the Indian Ocean is contributing to the stable air mass over the interior,” said Mary Scholes (University of the Witwatersrand) in an email. As global temperatures continue to climb this century due to human-produced greenhouse gases, Africa is expected to warm more quickly than the global average. Particularly high warming rates are expected over southwestern South Africa, Botswana, and Namibia, according to the chapter on Africa (PDF) in the 2014 Fifth Assessment Report (Working Group II) of the Intergovernmental Panel on Climate Change (IPCC). “Africa as a whole is one of the most vulnerable continents [to climate change] due to its high exposure and low adaptive capacity,” notes the report.


Figure 6. Infrared image of Tropical Storm Pali at 17Z (12 pm EST) Friday, January 8, 2015. Image credit: NOAA/NESDIS.

Tropical Storm Pali gathers strength in Central Pacific
The tropical depression located about 1400 miles southwest of Hawaii became Tropical Storm Pali on Thursday. Pali is the earliest tropical storm on record to develop between the International Date Line and the Americas (though one could argue the record-smashing 2015 tropical season in the Central Pacific has sloshed into 2016). As of 15Z (10 am EST) Friday, January 8, Pali’s top sustained winds had reached 55 knots (65 mph). Pali is embedded in a low-level trough between a westerly wind burst south of the equator and strong trade winds north of the storm, with easterly wind shear evident in satellite imagery. Pali’s northwestward motion is expected to slow to a crawl this weekend, after which the storm may bend back toward the south. The strong vertical wind shear (20 - 30 knots) and interactions with the surface trough are expected to gradually weaken Pali over the next several days.

In the Northwest Atlantic, a powerful nontropical low is stirring up the ocean west of Bermuda with a large area of strong winds, some as high as 65 mph. Models continue to move this system toward the east and southeast by early next week, which could put it in a more favorable environment for subtropical development. On Friday morning, the National Hurricane Center gave this system a 30% chance of subtropical or tropical development over the next five days.

Have a great weekend, everyone!

Bob Henson




Sunrise, Sunset / Sunrise, Sunset / Swiftly Flew 2014

Published: 1 janvier 2016
Sunrise, Sunset / Sunrise, Sunset / Swiftly Flew 2014

Here’s an easy prediction for 2016. When we arrive at March 1, 2016, it will have been 31 years since there was a month when the global average surface temperature was below the 20th century average. That’s a slight modification from the first sentence of what was either the last of 2014’s blogs or the first of 2015’s blogs (link to deathless prose). I generally leave the reporting of the current events to Jeff and Bob or those who are more on top of things at the The Capital Weather Gang. Plus, I took myself out of the monthly reporting of hottest month ever late last year, because I thought the real news would be if we had a month below the 20th century average. It is tiresome, for me, to keep saying how hot it is, when it is expected to be hot. And then there was that whole Godzilla El Niño thing, which worried me because I was unable to quantify one monster relative to another – and now this claim that this El Niño is not Godzilla. It’s a miracle I have any readers left.

Also in last year’s denouement, I wrote that despite it being cold in my backyard, in the middle of January we are very likely to receive the confirmation from NOAA that the previous year was, globally, the warmest year recorded. Same is true this year. (Where I am, in Colorado, it has been pleasantly frigid. Gives me faith in physics.) But I learned a long time ago that whether it is hot or cold in Colorado doesn't capture a lot of climate attention, so we have to rely on pine beetles and forest fires.

So despite my obtuse approach to today’s weather, I have been intrigued by The Storm That Will Unfreeze the North Pole. It comes at a time when I am finishing a video for a new project, where we talk about how the role of weather is to balance heat imbalances; that is, to carry warm air to the poles and to carry cold air away from the poles. This storm is truly noteworthy. (Update from Angela Fritz)

Now, the storm and the floods in the U.S. south central and Brazil definitely have a large influence of El Niño. Not so true for the floods in northern England. It seems pretty obvious at this point, that there is also a large influence of climate change, especially the warm oceans, and the amount of water that gets into the air to be rained upon the land. As Jeff and Bob have pointed out, the floods in Missouri are stunning for wintertime floods – this is, really, just rain, and big floods are usually the accumulation of many other factors.

I am lazy here on my last blog of 2014, and want to return to El Niño and California Drought: Simplistically. I had this quote about the El Niño of 1997-98, which for the U.S according to Ross et al. (1998), “was marked by a record breaking El Niño event and unusual extremes in parts of the country. Overall, the winter (December 1997- February 1998) was the second warmest and seventh wettest since 1895. Severe weather events included flooding in the southeast, an ice storm in the northeast, flooding in California, and tornadoes in Florida. The winter was dominated by an El Niño-influenced weather pattern, with wetter than normal conditions across much of the southern third of the country and warmer than normal conditions across much of the northern two-thirds of the country.”

I expect that Ross’ paragraph can be, largely, reused, and that the records can be tied to warmer oceans, more moisture, and more energy. And, then, we will be able to re-use this figure from Just Temperature, and show the continued trend of successive El Niños being associated with global records. A warm New Years to all. (Don’t worry, I have at least one more Exxon blog left in me.)



Figure 1: Global temperature differences with El Niño (warm) and La Niña (cool) years marked. From National Climatic Data Center.

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Thanks to Xandra for finding the update to the above figure. (We should probably go back and get the details on the first figure because it has some discernible differences. It was generated by WMO as well, as I recall.) And as expected, here it is:

Annual Global Temperature Anomalies 1950-2015 (for 2015, January to October)



Figure 2: Global annual average temperatures anomalies (relative to 1961-1990) based on an average of three global temperature data sets (HadCRUT.4.4.0.0, GISTEMP and NOAAGlobalTemp) from 1950 to 2014. The 2015 average is based on data from January to October. Bars are coloured according to whether the year was classified as an El Niño year (red), a La Niña year (blue) or an ENSO-neutral year (grey).Note uncertainty ranges are not shown, but are around 0.1°C.

Source: WMO, Press Release N° 13, 25 November 2015

I like this figure a lot because it separates out the largest source of global, internal variability and reveals trends in concert with the variability. It highlights the extraordinary scale of the 1997-98 El Niño. It will be interesting to see how this El Niño plays out through the Northern winter.
Categories:Climate Change

Common Thread at 2015 AGU Conference: The Big Melt

Published: 18 décembre 2015
The weather story of this month is the record warmth swaddling much of eastern North America and Europe. We’ll have much more to say about that next week, but keeping with the warm theme for today, I’ll share a couple of melt-related tidbits that drew my attention at this year’s Fall Meeting of the American Geophysical Union, which Jeff Masters and I attended this week. This is the world’s largest gathering of Earth-related scientists, with more than 20,000 researchers, journalists, and others in attendance. Thousands of posters and talks cover the whole spectrum of Earth sciences--at any one moment, there can be 50 or more presentations going on. Various science journalists and WunderBlog commentors have done a great job of capturing the broad array of science presented this week. You can browse the enormous number of abstracts at the meeting website. Many of the presentations were recorded and are now available through AGU On Demand (free registration is required). Here's a full list of those recorded sessions. (Thanks for WU member spbloom for the tip.] If the drip-drip-drip of climate change news starts getting to you, there’s a handy remedy: Jeff’s AGU post from Wednesday, “The Top Ten Reasons to be Hopeful on Climate Change”.

Lots of red on the Arctic Report Card
NOAA introduced its 2015 Arctic Report Card with a press conference on Tuesday, viewable in archive form (as are all of the press conferences). The Arctic’s grades were not good. Our northern polar regions are failing--that is, failing to shield themselves from the relentless build-up of greenhouse gases. The polar year running from October 2014 to September 2015 was the warmest in more than a century of recordkeeping, with the region now 3°C (5.4°F) warmer than it was at the start of the 20th century. The minimum summer extent of Arctic sea ice, which occurred on September 11, was not a record--it ranked fourth lowest in the satellite era (starting in 1979). However, the maximum winter extent did set a record low, and that occurred on February 25, two weeks ahead of average and the second earliest max in the satellite era.

One of the lesser-known but still profound changes to the Arctic is the decline in June snow cover, which is decreasing at around 18% per decade. Because the northern sun is at its strongest in June, this decline means that a good deal less sunlight is being reflected from polar regions, thus allowing more absorption of heat at the surface.



Figure 1. Top: Average temperature for October 2014-September 2015 compared to the 1981-2010 average. All around the Arctic, temperatures were much warmer than average, with only Greenland and a small part of northeastern Canada near or below average. Bottom: Annual temperatures for the Arctic (blue line, representing 60°N - 90°N) and the globe (black line) since 1900. Arctic temperatures are more variable from year to year than global temperatures (bigger swings above and below average). But despite the variability, a trend is clear: the Arctic has warmed more than the globe as a whole. Image credit: climate.gov.


Figure 2. Permafrost is thawing across the Arctic, causing northern lands to sink or change shape. In Gates of the Arctic National Park, a bank of this lake thawed in the summer of 2014, allowing the Okokmilaga River to cut through and drain it to sea. Researchers from the University of Alaska Fairbanks and the University of Colorado presented new work at the AGU Fall Meeting on the speeded-up pace of permafrost melt across northern Alaska. Image credit: Howcheng/US National Park Service/Wikimedia Commons.

More than polar bears at risk
Polar bears are the poster creatures of climate change, which makes it easy to overlook how warming temperatures might affect other Arctic creatures. These impacts can be difficult to pin down, because there are complicated intersections between human-driven warming and other anthropogenic factors, such as variations in hunting rates over time and the build-up of oil and gas infrastructure. An increase in rain-on-snow events over the Arctic is already having noteworthy impacts on reindeer, which forage for vegetation beneath snow cover during winter. A record number of reindeer (about 20% of a herd of 300,000) died in the winter of 2013-14 on the Yamal Peninsula of Western Siberia. A team led by Bruce Forbes (University of Lapland) described its post-event research in an AGU poster. “More than a year later, participatory fieldwork with nomadic herders during spring-summer 2015 revealed that the ecological and socio-economic impacts from this extreme event will unfold for years to come,” the group reported. They’re now investigating whether the loss of sea ice in the Barents and Kara Sea is playing a role in the growing prevalence of rain-on-snow events. “There is an urgent need to understand whether and how ongoing Barents and Kara Sea ice retreat may affect the region’s ancient and unique social-ecological systems.”

The state of Arctic walrus is analyzed in detail in this year’s Arctic Report Card. Sea ice is an integral part of walrus life: adults hang out and mate along the edges of pack ice in the winter, and mothers bear their young on ice in the spring. As sea ice retreats further from the shore of Chukchi Sea in late summer, walruses have been making dramatic “haulouts” over land, where young walrus are especially vulnerable to being trampled in the rush. An estimated 35,000 walruses clambered onto the coast at Point Lay, Alaska, in September 2014, and thousands more did the same in 2015. At the same time, some of the Arctic’s regional walrus populations have had a chance to rebuild their numbers in recent decades after years of largely unrestricted hunting. Walrus are at no immediate risk of extinction: there are at least 25,000 walruses in the high-latitude Atlantic, with many tens of thousands more in the Pacific. As sea ice continues to suffer, though, the concern is that the negative effects will put an increasing dent in walrus recovery. The Chuckchi Sea is now free of sea ice for about a month each year, but that may rise to several months later in this century.


Figure 3. A female walrus rests beside a yearling during a land-based “haulout” on September 19, 2013. The coastal walrus haulouts that form during periods of sea ice scarcity in the Chukchi Sea are composed primarily of adult female walruses and young, as well as some adult male walruses. Image credit: Ryan Kingsbery, USGS.

The big shift from snow to rain in Western mountains
Several posters examined the ongoing trend across the US West toward more winter rain and mixed-precipitation events and fewer all-snow events. Temperatures during winter and spring have warmed by roughly 2°C over the West since the 1950s. Michael Dettinger (USGS) extended prior work by others showing that most stations across the West are experiencing a larger fraction of their precipitation on days when no snow is reported. One of the best-instrumented locations in the West provides a closer look at this transition. More than three dozen precipitation stations with 55 years of data are scattered across the Reynolds Creek watershed of southwestern Idaho, which covers 93 square kilometers (about three times the size of Manhattan). Elevations vary from about 3000 to 6700 feet, so it’s easy for a winter storm to bring rain to lower elevations and snow to the higher terrain. Looking at the trends over the last three decades (1984 to 2014), Danny Marks (USDA) and colleagues found a doubling of the area in which most winter precipitation events arrived primarily as rain, and a halving of the area in which most of the events were primarily snow.

There will be far more rain than snow next week over the United States east of the Rockies, but one famously snowy city is on the verge of its first accumulation of the winter, which would fall atop green grass (see photo below). Buffalo, NY, received several hours of light snow on Friday afternoon, with a measurable amount possible before the evening is done. Update: Just before 7:00 pm EST Friday, Buffalo finally reported its first measurable snow of the season (0.1", the minimum amount that qualifies as measurable]. Prior to this year, the latest that Buffalo has seen its first 0.1” of snow for the winter was on December 3, 1899.

Steve Gregory has an update today on the long-range outlook beyond the impending holiday warmth. We’ll be back on Monday with a new post. In the meantime, have a great weekend, everyone!

Bob Henson



About the Blogs
These blogs are a compilation of Dr. Jeff Masters,
Dr. Ricky Rood, and Angela Fritz on the topic of climate change, including science, events, politics and policy, and opinion.
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