Tuesday, August 14, 2012

Must-Read Hansen: ‘Climate Change Is Here — And Worse Than We Thought’

By Joe Romm on Aug 4, 2012 at 2:24 pm
The nation’s best-known and most prescient climatologist, NASA’s James Hansen, has a must-read op-ed in the Washington Post.
Here’s how “Climate Change Is Here — And Worse Than We Thought” opens:
When I testified before the Senate in the hot summer of 1988, I warned of the kind of future that climate change would bring to us and our planet. I painted a grim picture of the consequences of steadily increasing temperatures, driven by mankind’s use of fossil fuels.
But I have a confession to make: I was too optimistic.
My projections about increasing global temperature have been proved true. But I failed to fully explore how quickly that average rise would drive an increase in extreme weather.
In a new analysis of the past six decades of global temperatures, which will be published Monday, my colleagues and I have revealed a stunning increase in the frequency of extremely hot summers, with deeply troubling ramifications for not only our future but also for our present.
This is not a climate model or a prediction but actual observations of weather events and temperatures that have happened. Our analysis shows that it is no longer enough to say that global warming will increase the likelihood of extreme weather and to repeat the caveat that no individual weather event can be directly linked to climate change. To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change.
I first wrote about this back in January when Hansen posted the draft of his findings, which made use of a detailed climatological analysis (see “Hansen et al: “Extreme Heat Waves … in Texas and Oklahoma in 2011 and Moscow in 2010 Were ‘Caused’ by Global Warming”).
Hansen has a good figure to show what’s happening:
Frequency of occurrence (vertical axis) of local June-July-August temperature anomalies (relative to 1951-1980 mean) for Northern Hemisphere land in units of local standard deviation (horizontal axis). Temperature anomalies in the period 1951-1980 match closely the normal distribution (“bell curve”, shown in green), which is used to define cold (blue), typical (white) and hot (red) seasons, each with probability 33.3%. The distribution of anomalies has shifted to the right as a consequence of the global warming of the past three decades such that cool summers now cover only half of one side of a six-sided die, white covers one side, red covers four sides, and an extremely hot (red-brown) anomaly covers half of one side.
Hansen’s climate analyses and warnings need to be heeded for two reasons. First, this analysis is supported by other recent papers, such as “Study Finds 80% Chance Russia’s 2010 July Heat Record Would Not Have Occurred Without Climate Warming” and “Nature: Strong Evidence Manmade ‘Unprecedented Heat And Rainfall Extremes Are Here … Causing Intense Human Suffering’.”
Second, Hansen has been right longer than almost anyone else around (see “Right for 27 years: 1981 Hansen study finds warming trend that could raise sea levels” and “Lessons From Past Predictions: Hansen 1981“).
Hansen’s mastery of climate science is quite literally what gives him climate prescience. We ignore him at our grave peril.
UPDATE: The AP’s excellent climate reporter, Seth Borenstein has a good piece up on Hansen’s new analysis, “New study links current events to climate change.” The AP has quotes from some credible independent experts:
The science in Hansen’s study is excellent “and reframes the question,” said Andrew Weaver, a climate scientist at the University of Victoria in British Columbia who was a member of the Nobel Prize-winning international panel of climate scientists that issued a series of reports on global warming.”Rather than say, ‘Is this because of climate change?’ That’s the wrong question. What you can say is, ‘How likely is this to have occurred with the absence of global warming?’ It’s so extraordinarily unlikely that it has to be due to global warming,” Weaver said….
Another upcoming study by Kevin Trenberth, climate analysis chief at the National Center for Atmospheric Research, links the 2010 Russian heat wave to global warming by looking at the underlying weather that caused the heat wave. He called Hansen’s paper an important one that helps communicate the problem….
White House science adviser John Holdren praised the paper’s findings in a statement. But he also said it is true that scientists can’t blame single events on global warming: “This work, which finds that extremely hot summers are over 10 times more common than they used to be, reinforces many other lines of evidence showing that climate change is occurring and that it is harmful.”
… Granger Morgan, head of engineering and public policy at Carnegie Mellon University, called Hansen’s study “an important next step in what I expect will be a growing set of statistically-based arguments.”
Here’s more from the Hansen op-ed:
The deadly European heat wave of 2003, the fiery Russian heat wave of 2010and catastrophic droughts in Texas and Oklahoma last year can each be attributed to climate change. And once the data are gathered in a few weeks’ time, it’s likely that the same will be true for the extremely hot summer the United States is suffering through right now.
These weather events are not simply an example of what climate change could bring. They are caused by climate change. The odds that natural variability created these extremes are minuscule, vanishingly small. To count on those odds would be like quitting your job and playing the lottery every morning to pay the bills.
Twenty-four years ago, I introduced the concept of “climate dice” to help distinguish the long-term trend of climate change from the natural variability of day-to-day weather. Some summers are hot, some cool. Some winters brutal, some mild. That’s natural variability.
But as the climate warms, natural variability is altered, too. In a normal climate without global warming, two sides of the die would represent cooler-than-normal weather, two sides would be normal weather, and two sides would be warmer-than-normal weather. Rolling the die again and again, or season after season, you would get an equal variation of weather over time.
But loading the die with a warming climate changes the odds. You end up with only one side cooler than normal, one side average, and four sides warmer than normal. Even with climate change, you will occasionally see cooler-than-normal summers or a typically cold winter. Don’t let that fool you.
Our new peer-reviewed study, published by the National Academy of Sciences, makes clear that while average global temperature has been steadily rising due to a warming climate (up about 1.5 degrees Fahrenheit in the past century), the extremes are actually becoming much more frequent and more intense worldwide.
When we plotted the world’s changing temperatures on a bell curve, the extremes of unusually cool and, even more, the extremes of unusually hot are being altered so they are becoming both more common and more severe.
The change is so dramatic that one face of the die must now represent extreme weather to illustrate the greater frequency of extremely hot weather events.
Such events used to be exceedingly rare. Extremely hot temperatures covered about 0.1 percent to 0.2 percent of the globe in the base period of our study, from 1951 to 1980. In the last three decades, while the average temperature has slowly risen, the extremes have soared and now cover about 10 percent of the globe.
This is the world we have changed, and now we have to live in it — the world that caused the 2003 heat wave in Europe that killed more than 50,000 people and the 2011 drought in Texas that caused more than $5 billion in damage. Such events, our data show, will become even more frequent and more severe.
My only (slight) disagreement with Hansen is on matters of policy:
There is still time to act and avoid a worsening climate, but we are wasting precious time. We can solve the challenge of climate change with a gradually rising fee on carbon collected from fossil-fuel companies, with 100 percent of the money rebated to all legal residents on a per capita basis. This would stimulate innovations and create a robust clean-energy economy with millions of new jobs. It is a simple, honest and effective solution.
We agree on the need for a significant and rising price on carbon through what he calls a fee but which is the political equivalent of a tax. He thinks all the money has to be given back to the public to win popular support.
I generally think popular support has not been the problem, whereas business support has. Also, we have a massive deficit, so we at least have to leave open the possibility that some of the money collected will go toward deficit reduction.
In any case, it doesn’t really matter whether I am right or Hansen is as long as everyone is flexible in achieving the most important goal the rising carbon price, since the final deal will no doubt require compromises across the board.
But who can argue with his final statement?
The future is now. And it is hot.

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