science

InterAcademy Council Completes Review of IPCC Report Process

You might recall earlier this year that a few mistakes were discovered in the Intergovernmental Panel on Climate Change’s (IPCC) 3,000-page assessment report published in 2007. The mistakes did nothing to undermine the report’s major findings: It is unequivocal that the climate is changing, and there is greater than 90 percent certainty that most of the observed warming of the past half-century is due to human influences. Earlier this year, I discussed the errors on E&ETV’s On Point program.

Climate Risks: Lessons from 2010’s Extreme Weather


Update: Dr. Jay Gulledge is featured on National Journal's Energy & Environment Expert Blogs. Click here to read Dr. Gulledge's take on Climate Risks Here and Now

Last fall I posted a blog about the unusual number and severity of extreme weather events that have been striking around the globe for the past several years. That entry focused on the alternating severe drought and heavy flooding in Atlanta in 2007-2009 as an example of the roller coaster ride that climate change is likely to be. As every dutiful scientist does, I stopped short of blaming those individual weather events on global warming, but I am also careful to point out that it is scientifically unsound to claim that the confluence of extreme weather events in recent years is not associated with global warming; I’ll return to this question later.

Tempestuous 2010

The weather of 2010 continues the chaos of recent years. In the past six months, the American Red Cross says it “has responded to nearly 30 larger disasters in 21 [U.S.] states and territories. Floods, tornadoes and severe weather have destroyed homes and uprooted lives …” Severe flooding struck New England in March, Nashville in May, and Arkansas and Oklahoma in June.

"Facts are Stubborn Things ..."

In his defense of soldiers in the Boston Massacre trials, John Adams went on to say “… and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence.”

No matter what we may wish were happening, no matter what spin some may try to sell, the clear evidence of climate change continues to mount.

The U.S. National Oceanic and Atmospheric Administration (NOAA) has just released its annual report on the state of the climate, and the facts speak volumes about the pervasiveness and speed of actual climate change, not model projections. 

"Climategate" Scientists Exonerated

I posted previously on the controversy surrounding emails that were hacked from a computer server at the University of East Anglia’s (UEA) Climatic Research Unit (CRU) in the U.K. The emails revealed the private exchanges of several prominent climate scientists dealing with their science and their reactions to climate change deniers who requested access to their private computer files and intellectual property. The contents of the emails suggested to the untrained eye that the scientists had manipulated data and tried to undermine the scientific peer-review process. From my reading of the emails, I judged that nothing of the sort had happened. Since my last writing on the topic, five separate independent investigations (3 in the United Kingdom and 2 in the U.S.) of the matter have concluded that there was no mishandling of data or other wrongdoing beyond some foot-dragging in response to Freedom of Information requests by climate change deniers. The clear message from these investigations is that proper scientific methods were followed and the integrity of climate science remains solid as a rock. 

Comprehensive Climate Science Reports Released Today

Today the National Academy of Sciences (NAS) released three of its long-awaited “America’s Climate Choices” (ACC) reports. A fourth report will be released later this year, as will an overarching synthesis report. The three reports released today focused on advancing the science of climate change, adapting to unavoidable climate change, and limiting the ultimate extent of climate change. The reports and background information on the study are accessible from the ACC web site.

Collectively, the ACC reports are the most comprehensive study the NAS has conducted on climate change. The project was mandated by Congress and requested by the National Oceanographic and Atmospheric Administration in 2008. Unlike past NAS efforts, the ACC reports emphasize how the nation can move forward on solving the climate change problem.

NAS president Ralph J. Cicerone said, “These reports show that the state of climate change science is strong.” The study emphasizes that our current understanding of human-induced climate change is supported by many independent lines of evidence that have weathered intense debate and serious exploration of alternative explanations: “Climate change is occurring, is caused largely by human activities, and poses significant risks for – and in many cases is already affecting – a broad range of human and natural systems,” the report says.

A statement about the ACC by our center's president Eileen Claussen is available here.

We will be sure to let you know when the remaining pieces of the ACC report come out later this year.

Jay Gulledge is Senior Scientist and Director of the Science & Impacts Program

Monitoring Planet Earth’s Vital Signs

While the Senate’s effort to take up comprehensive clean energy and climate legislation remains on hold awaiting a resolution of when and if an immigration bill will be considered, EPA just issued a new report that sends a loud and clear reminder about why Congressional action is urgent.  The report, Climate Change Indicators in the United States, presents detailed information documenting 24 different ways in which climate change is altering our nation and the world.

This is not your standard climate report with pages and pages of scenarios and model runs projecting out over time what future climate impacts are possible.  Instead, this report looks back and documents biological and physical changes that have already occurred.  It focuses on actual measurements of real conditions – from increases in greenhouse gas concentrations measured in the atmosphere to changes in sea surface temperatures to shifts in the length of growing seasons.

Weather vs. climate, and what a difference a few degrees can make

There seems to be some confusion out there about weather vs. climate.  For example, a Virginia Republican Party video urged citizens to call their Congressmen and tell them how much global warming they got during the big snowstorm a couple of weeks ago. But that doesn’t really make any sense.  In simple terms, weather determines whether you need to take an umbrella with you today; climate determines whether you need to own an umbrella.  Weather determines whether you need your down coat today; climate determines whether you need to own a down coat.  Weather determines whether you turn on your air conditioning unit today; climate determines whether you own an air conditioner.  Weather determines whether the plants in your garden have a good day; climate determines what plants will likely thrive in your local environment. 

Climate is the long-term average of weather.  Weather changes all the time; climates are generally fairly stable, allowing us to make long-term decisions based on the notion that the future climate will be like the past.  One unusual weather event does not mean the climate is changing. But many unusual weather events could mean the climate is changing. And climate change will mean that on average, the weather we will have in the future will be different from what we had in the past.   That could even mean that record-breaking snowfall events happen more and more often in Virginia and Washington, D.C.

Update #2: It’s so cold! What happened to global warming?

Science Q&A

In the past few weeks I’ve posted twice (here and here) on reasons why global warming could be increasing the frequency of heavy snow events in certain parts of the United States (and likely in other similarly situated places around the world).

In a recent post on his WunderBlog (Weather Underground Blog), Dr. Jeff Masters gives his take on this issue. Dr. Masters is co-founder and Director of Meteorology of Weather Underground, a weather service that provides real-time weather information via the Internet. Unlike me, he’s a real weather expert and I highly recommend his blog.

Update: It’s so cold! What happened to global warming?

Science Q&A

The cold weather continues across much of the Unites States, Europe, and central Asia as the Arctic Oscillation remains in a strong “negative” state, forcing cold Arctic air down to the mid-latitudes. A couple of weeks ago I explained why more frequent heavy snowfall events could be a consequence of global warming for mid-latitude areas near large bodies of water, like Washington, D.C., and Syracuse, New York (see figure).

The average amount of annual snowfall has been increasing in Syracuse, New York, for most of the past century. (SOURCE: Increasing Great Lake–Effect Snowfall during the Twentieth Century: A Regional Response to Global Warming? Journal of Climate vol. 16, pp. 3535-3342, Figure 1)

On January 31, I noticed a forecast for lake-effect snowfall around the Great Lakes on Weather.com:  “Lake-effect snows are also possible near the central and western Great Lakes today and tonight.”

It’s so cold! What happened to global warming?

Science Q&A

On December 19, Washington, D.C. was buried by two feet of snow, setting a new record for snowfall during the entire month of December and paralyzing the city for three days.  As my neighbor and I shoveled out from the storm, he stopped for a moment, grinned, and asked, “So what happened to global warming?” Boy was he surprised when I said, “Glad you asked,” and launched into a 15-minute oratory on why global warming might mean more, not less, extreme snowfall for some parts of the world.

Before continuing, I need to reiterate that no single weather event can be attributed to global warming. So the question here is not, “What caused the heavy snowfall on December 19?” The question is, “Is heavy snowfall or unusually cold weather inconsistent with global warming?”

You need two things to create heavy snowfall: moist air and cold air. The two generally don’t occur in the same air mass because cold air can’t hold much moisture. So you need two air masses, one that is warm and moist and one that is cold and dry, to collide with each other. That is exactly what happened over the Mid-Atlantic region on December 19.

This condition is not only consistent with global warming, but it can be expected to occur more frequently in certain places as a direct result of global warming. It takes warmth to generate moist air. First, you need warmth to evaporate enough water from lakes or oceans to generate a massive snowstorm. Second, you need warm air to keep the water vapor aloft so that it doesn’t rain out before it finds a cold air mass to collide with. When I asked weatherman Joe Witte where the moisture that ended up in my snow shovel came from, he said, “Some of the moisture came out of the Gulf of Mexico AND some from the warm Atlantic ocean with the VERY warm (70s!) Gulf Stream along the East coast acting as a hot plate for evaporation of moisture into the cold dry air.”

(SOURCE:  NOAA polar-orbiting satellite data compiled by Rutgers University Coastal Ocean Observation Lab)


Although the past few weeks have been very cold in the eastern United States, Joe pointed me to NOAA satellite measurements that found sea surface temperatures in the Gulf of Mexico and the Atlantic Ocean to be 1 to 3 °F warmer than normal during the week before the big snowstorm hit (see figures above). There is strong scientific evidence showing that, on average, the oceans are warmer today than they were a century ago because of human-induced global warming. So the warm ocean temperatures that fed the heavy snowfall are consistent with global warming. In fact, because of global warming, we should expect such conditions to be more common today than in the past and even more common in the future as warming continues.

So where did the cold, dry air come from? Global warming is about changes in long-term averages and not about single events; it does not mean an end to cold weather. Instead, it means that cold weather will become less frequent and hot weather more frequent when averaged over decades. In fact, both of these trends have been observed over the past 50 years in the United States and globally. So, even with global warming we will have cold winters, just fewer of them. It is also important to remember that a cold winter here doesn’t mean a cold winter everywhere. In fact, many parts of the world, including the Arctic and the tropics, are having an unusually warm winter. The current cold snap is concentrated in the mid-latitudes of the northern hemisphere, and there will always be the potential  for cold Arctic air masses to visit the mid-latitudes from time to time.

The current cold snap is related to a known weather pattern called the Arctic Oscillation. When the Arctic Oscillation switches between “positive” and “negative” states, it simply shifts heat between the Arctic and the mid-latitudes. Scientists call this kind of pattern “internal variability,” and it does not change the total amount of heat in the climate system. Internal variability can create strong differences in the weather from year to year and place to place, but these shifts average out to zero net climate change over decades. Only a net change in the total amount of heat in the climate system can change the long-term average climate, and that is the nature of global warming.

When the mid-latitudes get periodic blasts of cold Arctic air, global warming makes it more likely that the cold air from up north will collide with moist, warm air from down south, creating more heavy snowfall events in mid-latitude areas near large bodies of water. A similar phenomenon is affecting the Great Lakes region. Syracuse, New York is one of the snowiest places in the country, but it and other areas around the Great Lakes are getting even snowier! Because the Great Lakes are getting warmer, they are icing over later and melting earlier than they used to. Without the ice, water can evaporate and enter the atmosphere over the lakes later in the fall and earlier in the spring. When winds blow this moist air over the land where temperatures are lower, we get the famous “lake effect” snow. With more open water during the winter, more lake effect snow is falling.

These are the cold facts of global warming.

Jay Gulledge is Senior Scientist and Program Manager for Science & Impacts

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