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NASA study links extreme heat to global warming

posted 7 Aug 2012, 07:24 by Mpelembe   [ updated 7 Aug 2012, 07:25 ]

Scientists from the National Aeronautics and Space Administration (NASA) have published the first empirical study linking extreme heat events of recent years to global warming. The study's author and head of NASA's Goddard Institute for Space Studies, Dr. James Hansen says the research demonstrates conclusively that warmer temperatures are linked to a cycle of climate change.

The wildfires now burning in parched Oklahoma have spread largely as a consequence of a heatwave last year. According NASA climate scientist Dr. James Hansen, that heatwave was part of an unusual warming pattern that has emerged over the past sixty years.
In his paper, titled "The New Climate Dice: Public Perception of Climate Change" Dr. James Hansen paints a stark picture of temperature change over more than fifty years.

At a news conference in New York on Monday (August 6) Hansen said that the frequency of unusually warm summers is increasing. He says the phenomenon is almost certainly the result of global warming.

"The frequency of anomalous temperatures is changing such that we're getting more and more unusually warm seasons, fewer unusually cool seasons but most importantly the tail of the distribution, the extremely warm seasons are occurring at a noticeable frequency," Hansen told Reuters.

The study used observed temperatures from 1951 to 2011- not climate models - to confirm climate change's role in causing specific extreme weather events.

To illustrate long term climate change, Hansen came up with the analogy of the "climate dice" in 1988 to describe the chances of warm and cool seasons.

Since local weather is variable from day to day and year to year, he looked at the frequencies in which abnormal temperatures occur.

In 1980 there was an equal chance of getting regular temperatures to extremely hot to extremely cold temperatures. The dice was two sides white, two sides red and two sides blue.

In the past 30 years however, the data has changed the look of the dice. Hansen says it is now loaded towards red, indicating evidence of rapid global warming.

"If we look at the data now it's about four-and-a-half sides that are red," Hansen said.

"But what's more important and what I really hadn't thought about in the 1980s was the fact that as we're pushing this distribution of anomalous temperatures toward the hotter and hotter, the tail of the distribution is going to become extremely hot. That's what is the kind of event that we're seeing in the Midwest this year and we saw in Oklahoma and Texas last year and associated with these very high temperatures are going to be the wild fires and the extreme drought."

The study says that the portion of the land affected by extreme heat in the base period between 1951 and 1980 was 0.2 percent of the Earth's surface. This number says Hansen, has increased to approximately 10 percent of the Earth's surface in the last decade.

Extremely hot summers - those with temperatures three standard deviations greater than the mean temperature - occurred much more frequently in the past several years than during the base period, when they were practically absent.

This includes the devastating drought in Texas and Oklahoma in the summer of 2011 and the summer of 2010 in Moscow when smog, fuelled by wildfires filled the Russian capital.

Hansen cautioned that extremely hot summers could become the norm and possibly contribute to extreme droughts and floods in the future if fossil fuel consumption isn't curbed.

"There is consensus that the planet is getting warmer because the atmospheric composition is changing. Principally that's carbon dioxide from burning fossil fuels. What's become clear is that if we were to burn all of the fossil fuels, than we would create a completely different planet. We simply can't do that, and yet the policies do not yet take account of that. We're going after every fossil fuel we can find," he said.

But not all climate scientists agree with Hansen's assertion that the heatwaves would not have occurred in the absence of global warming, something they say is very difficult to substantiate conclusively.

Hansen however, is certain that global warming is responsible and humans have the ability to mitigate its impact.

"If we act soon I think we can still avoid the worst consequences like multi-meter sea level rise and the things, that would - a large fraction of the cities are located on the coastlines around the world. We don't want the ice sheets to disintegrate. The economic implications would be unbelievable."

Hansen says those implications are already being felt. He points to the drought now gripping much of the United States, the worst in 55 years.

Major farm states including Illinois, Nebraska, Kansas, Missouri and Iowa, have experienced temperatures 5 to 10 degrees (Fahrenheit) above normal in recent weeks.

The United States is the world's largest exporter of corn, wheat and soybeans and continuing drought in the U.S. farm belt may result in higher prices for poor people around the world, according the International Food Policy Research Institute, an agricultural think tank.

Hansen and his co-authors say continued warming could potentially make extremely hot summers the norm and possibly contribute to extreme droughts and floods.