Tag Archives: Climate history

In climate change, heat extremes tell a bigger story than average temps

News reports about climate change often focus on how the average global temperature is rising, but perhaps more attention should be paid to some alarming trends in extreme temperatures — the conditions that are more likely to kill people and push species toward extinction.

From 1986 to 2015, hottest-day-of-the-year readings climbed by 0.25 degrees Celsius per decade, the UCI study found. Some megacities saw a rise of 0.60 degrees Celsius per decade.
Map: Simon Michael Papalexiou, UCI

A new study published last week revealed that temperatures across the Earth’s surface went up an average of 0.19 degrees C (.34° F) each decade over the past 30 years, whereas the highest temperature recorded each year has gone up even more — an average of 0.25 degrees C (0.45° F) per decade.

The study, led by Simon Papalexiou of the University of California at Irvine, calls out even greater changes in the extreme temperatures in specific locations. Average change per decade of 0.33 degrees C (0.59° F) were measured in some parts of Europe, Asia, Australia and Africa. Download PowerPoint map (PPT 1.4 mb) from the report in the journal Earth’s Future.

Meanwhile, hottest temperatures recorded throughout the world grew even faster in some of the largest cities, according to the study. Of the cities for which reliable data are available, the increased temperature in the “megacities” rose an average of 0.33 degrees C (.59° F) per decade, and numerous cities exceeded 0.6 degrees C (1.08° F).

Over a 50-year time period, Paris had the fastest change, with the hottest temperature of the year growing by 0.96 degrees C (1.73° F) per decade. Over the past 30 years, Houston’s hottest temperatures grew even faster, rising 0.99 degrees C (1.8° F) per decade.

The urban heat island effect, which is caused by solar heat absorption in concrete, steel and glass structures, is “likely to have contributed to the observed alarming changes,” the report says, adding that a better understanding of the causes could help reduce the risks for people living in cities.

“More than just temperature readings on a map, these events have taken a severe human toll,” states a UCI news release on the paper. “A heat wave in Europe in 2003 caused roughly 70,000 deaths, and another in Russia in 2010 killed nearly 55,000 people. In the United States, an average of 658 deaths due to excessive heat were reported per year between 1999 and 2009.”

Amir AghaKouchak, a co-author of the study, said government officials will need to pay more attention in the megacities, where the risks are greatest.

“In France after that massive heatwave (in 2003), now all nursing homes or places where there are a lot of vulnerable people have to have at least a common room with air conditioning,” said AghaKouchak, quoted in a Reuters story by reporter Laurie Goering.

“That can be done and it’s already happening in some places,” he said. “But some countries don’t have the resources to do that.”

Architectural styles and green areas with trees and plants may help reduce the everyday risks to those who don’t have the resources to protect themselves.

The greatest problems surrounding climate change won’t be seen in the averages but in the new extremes — the temperatures, sea levels and rainy downpours never before experienced at a given location.

The website WX shift (pronounced “weather shift”) was designed to tell people about changing climate trends, including “The 10 hottest years.” For example, of the 10 hottest years on record, only two occurred before 1998 (1934 and 1990). The five hottest years on record have all occurred in the past 11 years.

WX shift also contains predictions for the number of days a given location will reach a high temperature. See “Future days above 95° F. This interactive graphic is said to be based on historical records and climate change models, as explained at the bottom of the page.

Another graphic on Climate Central’s website helps explain how a small change in average temperature can lead to an increasing number of record-breaking temperatures and more extreme conditions.

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Weather extremes now surpassing the realm of natural possibilities

A new report from the American Meteorological Society makes a rather stunning statement about climate change. For the first time, researchers have concluded that specific weather-related events could not have happened without the influence of climate change caused by human activity.

Three events studied in 2016 were so extreme that they did not fit into the context of natural climate conditions, according to researchers working on separate projects. One involved the global heat record for 2016; another was focused on warmth across Asia; and the third was the “blob” of warm ocean water familiar to folks who follow weather in the Pacific Northwest.

A “blob” of warm water off the Northwest coast from 2013 to the end of 2016 could not have occurred without human-induced climate change, experts say.
Map: NOAA’s Earth System Research Laboratory

“This report marks a fundamental change,” said Jeff Rosenfeld, editor-in-chief of the Bulletin of the American Meteorological Society, in a news release. “For years scientists have known humans are changing the risk of some extremes. But finding multiple extreme events that weren’t even possible without human influence makes clear that we’re experiencing new weather, because we’ve made a new climate.”

Personally, I did not expect to see this sort of demonstrable statement about man-made climate change anytime soon. In classes and seminars on the subject of climate change, I’ve often seen lecturers present frequency curves that show the number of times that certain weather-related phenomena — such as temperatures or rainfall — are observed over a given time.

We’re told by climatologists that many of these curves are steadily shifting, so that fairly extreme conditions occur more often and truly extreme conditions emerge for the very first time in certain locations.

Researchers are loathe to say that a given storm, drought or hurricane is the result of climate change. They would rather say climate change affects the likelihood of extreme weather events, plotted at the end of the frequency curve. In the realm of statistics, there is a tendency to hold onto the idea that almost any kind of weather could occur almost anytime, provided that a perfect storm of conditions line up together.

Against that backdrop, comes the new report titled “Explaining extreme events of 2016 from a climate perspective,” which examines extreme weather events throughout the world.

“First, it is important to note that climate scientists have been predicting that … the influence of human-caused climate change would at some point become sufficiently strong and emergent to push an extreme event beyond the bounds of natural variability alone,” state the six editors in an introduction to the report.

“It was also anticipated that we would likely first see this result for heat events where the human-caused influences are most strongly observed,” they continue. “It is striking how quickly we are now starting to see such results, though their dependence on model-based estimates of natural variability … will require ongoing validation …”

In other words, the conclusion comes from computer models that can analyze the probability of an extreme event taking place when greenhouse gases are found at different concentrations. Results using today’s observed conditions are compared with results using conditions before the industrial release of greenhouse gases.

In the three highlighted papers, the researchers calculated the “fraction of attributable risk,” or FAR, for the extreme event they were studying. FAR is a statistical approach used in epidemiology to measure the likelihood of an event under various conditions. For explanations, see Boston University School of Public Health and the 2007 IPCC report.

“All three papers concluded that the FAR was 1, meaning that the event was not possible in the ‘control’ planet and only possible in a world with human-emitted greenhouse gases,” the editors say.

Although this is the first time that researchers have concluded that extreme events could not have happened without human-induced climate change, the editors are quick to point out that the same phenomenon may have occurred unnoticed in the past on a smaller geographic scale.

These findings do not mean that the climate has reached any kind of tipping point. It simply adds to the evidence that mounting weather extremes are not the result of natural processes.

Reporters Brad Plumer and Nadja Popovich of the New York Times do a nice job of delving into the concept of attribution science while mentioning five of the extreme events covered in the new report. They quoted Heidi Cullen, chief scientist at Climate Central, which produces news stories about climate issues.

“In 2011, people were still of the mind-set that you couldn’t attribute any individual event to climate change,” Cullen said. “But with each subsequent issue (of the BAMS report), people are able to say that climate change really is increasing the risk” that extremes will occur.

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Northwest stayed warm in May; new graphics show long-term trends

After warmer-than-average temperatures for much of the past year, May suddenly turned cooler across the nation — except for the Northwest, which remained warmer than normal.

Temp anomaly

Although it seemed cool recently, at least compared to April, Western Washington had the greatest deviation with temperatures between 3 and 5 degrees higher than the 30-year average. See first map.

It seems ironic to write about cooler temperatures after last month’s teaser headline at the top of the Kitsap Sun’s front page: “Earth getting HOT, HOT, HOTTER!”

The big story earlier this month was that worldwide temperatures had broken all-time heat records for 12 months in a row, and April’s record-high temperature was a full half-degree higher than the previous record.

The average temperature hasn’t been below the 20th century average since December 1984, and the last time the Earth broke a monthly cold record was nearly a century ago, in December 1916, according to NOAA records.

“These kinds of records may not be that interesting, but so many in a row that break the previous records by so much indicates that we’re entering uncharted climatic territory (for modern human society),” Texas A&M University climate scientist Andrew Dessler wrote in an email to Seth Borenstein of the Associated Press.

Temp outlook

El Niño, which is now fading, was blamed in part for the unprecedented heat worldwide. But climatologists say the onward march of global warming lies in the background. Last year turned out to be the hottest year on record, easily beating 2014, which was also a record year.

The first four months of this year were so much hotter than 2015 that 2016 is still likely to set another record. NOOA’s Climate Prediction Center says La Niña conditions are on the way, with a 50 percent chance of La Niña by summer and a 75 percent chance by fall.

Summer temperatures are expected to be above average except in the Central U.S., while both coasts are expected to be the most likely to exceed normal temperatures. Check out the second map on this page.

Speaking of the onward march of climate change, computer graphics developers keep coming up with new ways to show how global temperatures are increasing in concert with rising greenhouse gases in the atmosphere.

New normal

Climate Central has combined data sets from NOAA to produce the orange graph,which shows the advance of a trailing 30-year temperature average from 1980 through 2015. To put it simply, we continue to adjust to a new normal.

Others have used animation to depict temperature change. One graphic (below) received a lot of attention this month. Temperature change is represented as the distance from a “zero” circle starting in 1850. Each month, a line moves one-twelfth of the way around the circle, completing 360 degrees each year. The line gets farther and farther from the center and really jumps outward in 2015.

Ed Hawkins, professor of meteorology at the University of Reading near London, created the animation. He credited an associate, Jan Fuglestvedt, with the idea of a spiral.

Jason Samenow, chief meteorologist for the Washington Post’s Capital Weather Gang, called it “the most compelling global warming visualization ever made.” His blog post also includes some other visual depictions of climate change.

Another animated graph, by Tom Randall and Blacki Migliozzi of Bloomberg, show similar data depicted as a moving line graph.

NOAA Visualizations plotted temperature differences at various locations on a world map. Over time, it is easy to see how the Earth has gotten generally warmer, accelerating in recent years.

One of the most intriguing graphics, in my opinion, is one that purports to show the various factors that affect global temperature — from volcanic activity to man-made aerosols to greenhouse gases. The designers, Eric Roston and Blacki Migliozzi of Bloomberg, ask viewers to judge which factor they believe leads to global warming.

Since this is a blog about water issues, I would probably be remiss if I didn’t point out that the consequences of rising greenhouse gases is not just an increase in the Earth’s temperature. We can’t forget that a major portion of the carbon dioxide is being absorbed into the ocean, causing effects on marine life that are far from fully understood.

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Puget Sound farmers expected to change as climate changes

I’ve been going through the new report about climate change in the Puget Sound region, and I can tell you that the most optimistic chapter is the one on farming. Check out the story I wrote for the Encyclopedia of Puget Sound.

To be sure, farmers will have plenty of problems to contend with. Rising sea levels and more intense rainstorms will probably causing flooding and seawater intrusion where it has never been seen before. Some of today’s farmland could become unsuitable for agriculture, and drier summers will force much better management of limited water supplies.

Temperatures are rising in the Puget Sound lowlands. Graphic: Climate Impacts Group
Temperatures are rising in the Puget Sound lowlands. // Graphic: Climate Impacts Group

But as the climate undergoes change, farmers can change with the climate, growing crops suitable for the conditions they face, said Kelly McLain, senior natural resources scientist with the Washington Department of Agriculture.

“Farmers are extremely adaptable,” Kelly told me. “I think water is going to be the limiting factor for almost all decisions.”

It’s hard to find that kind of optimism anywhere else when it comes to climate change in the Puget Sound region. The story I wrote to accompany last week’s release of the new report discusses the likelihood that landslides will increase because of more intense rainfall patterns. See “Shifting ground: Climate change may increase the risk of landslides” and the Water Ways post on Nov. 19.

My third and final story in the series, which will be published next week, talks about coming changes in habitats — and thus species — expected in Puget Sound as air temperatures increase, sea levels rise, rainstorms grow more intense and oceans undergo acidification.

Total annual precipitation does not appear to be changing in the Puget Sound region. Graphic: Climate Impacts Group
Total annual precipitation does not appear to be changing in the Puget Sound region.
Graphic: Climate Impacts Group

I took on this writing project as part of my work for the Puget Sound Institute, which publishes the Encyclopedia of Puget Sound. PSI commissioned the climate report with funding from federal and state governments. The Climate Impacts Group at the University of Washington compiled the best scientific knowledge into a very readable report, which can be found on the encyclopedia’s website or on the website of the Climate Impacts Group.

One interesting chapter of the report, called “How is Puget Sound’s Climate Changing?” (3 mb) supports the understanding that climate change is not something we need to wait for. It’s something that scientists can measure now, although climatologists expect the changes to come faster as atmospheric carbon dioxide levels increase.

Here are a few of the changes that can be measured, along with a bit of explanation about the uncertainty:

  • Average air temperatures have been increasing in the Puget Sound lowlands and are currently about 1.3 degrees higher than in 1895. Higher temperatures have been found to be statistically significant for all seasons except spring, with the overall increase shown in a range between 0.7 to 1.9 degrees F.
  • Nighttime air temperatures have been rising faster than daytime temperatures. Nighttime lows have been increasing by about 1.8 degrees since 1895, while daytime highs have been increasing by about 0.8 degrees.
  • The frost-free season has lengthened by about 30 days (range 18-41 days) since 1920.
  • As in other areas, short-term trends can differ substantially from long-term trends. Cooling observed from 2000-2011, for example, has not altered the long-term temperature increase.
  • An ongoing debate questions how much, if any, of the long-term warming trend is a result of natural climate variability. One study says up to 80 percent may be natural, caused by atmospheric circulation, not by greenhouse gas buildup. Other researchers have been unable to replicate the findings for other data sets.
  • Total annual precipitation does not appear to be increasing or decreasing over a long time scale. Spring precipitation has increased at a statistically valid 27 percent for the months March through May.
  • Most studies are finding modest increases in the frequency and intensity of heavy precipitation compared to historical levels, but results depend on the time period and methods of analysis.
  • Ongoing variability in weather patterns related to El Nino and the Pacific decadal oscillation will continue to strongly influence temperature and precipitation for relatively short periods. It is not clear how long-term climate change will interact with these more variable climate patterns.

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