Trenberth: “It’s not the right question to ask if this storm or that storm is due to global warming, or is it natural variability. Nowadays, there’s always an element of both.”
The summer’s heat waves baked the eastern United States, parts of Africa and eastern Asia, and above all Russia, which lost millions of acres of wheat and thousands of lives in a drought worse than any other in the historical record.
Seemingly disconnected, these far-flung disasters are reviving the question of whether global warming is causing more weather extremes.
The collective answer of the scientific community can be boiled down to a single word: probably.
That’s the opening of “In Weather Chaos, a Case for Global Warming!” It is one of the better recent major media articles on global warming and extreme weather — and the best front page New York Times climate article in years.
The NYT is clearly making a major statement since not only is this “above the fold,” but it takes up most of the front page with large photos of what’s happening in Pakistan and Russia and the U.S. (see Russian Meteorological Center: “There was nothing similar to this on the territory of Russia during the last one thousand years in regard to the heat.” and Hottest* July in RSS satellite record, record floods swamp Pakistan, U.S. set 1480 temperature records in past two months, and 2010 breaks 2007 record for most nations setting all-time temperature records):
Lots of good stuff in the story:
“The climate is changing,” said Jay Lawrimore, chief of climate analysis at the National Climatic Data Center in Asheville, N.C. “Extreme events are occurring with greater frequency, and in many cases with greater intensity.”
He described excessive heat, in particular, as “consistent with our understanding of how the climate responds to increasing greenhouse gases.”
Theory suggests that a world warming up because of those gases will feature heavier rainstorms in summer, bigger snowstorms in winter, more intense droughts in at least some places and more record-breaking heat waves. Scientists and government reports say the statistical evidence shows that much of this is starting to happen.
But the averages do not necessarily make it easier to link specific weather events, like a given flood or hurricane or heat wave, to climate change. Most climate scientists are reluctant to go that far, noting that weather was characterized by remarkable variability long before humans began burning fossil fuels and releasing greenhouse gases into the atmosphere.
“If you ask me as a person, do I think the Russian heat wave has to do with climate change, the answer is yes,” said Gavin Schmidt, a climate researcher with NASA in New York. “If you ask me as a scientist whether I have proved it, the answer is no “” at least not yet.”
That is a distinction always worth remembering. The scientific literature is primarily filled with that which can be proven — and most climate scientists are unwilling to make public statements that go beyond what can be proven. That is a key reason so much of the scientific literature is conservative or understates what is likely to come on our current path of unrestricted emissions. And that goes double for reviews of the scientific literature that must be signed off on word for word by major governments, like the IPCC.
That’s why talking to lots top climate scientists is so important for reporters or anyone who want to understand what is coming. That’s how you learn what they really believe and what they expect will appear in the scientific literature in the coming years.
Here’s more from the NYT:
In Russia, that kind of scientific caution might once have been embraced. Russia has long played a reluctant, and sometimes obstructionist, role in global negotiations over limiting climate change, perhaps in part because it expected economic benefits from the warming of its vast Siberian hinterland.
But the extreme heat wave, and accompanying drought and wildfires, in normally cool central Russia seems to be prompting a shift in thinking.
“Everyone is talking about climate change now,” President Dmitri A. Medvedev told the Russian Security Council this month. “Unfortunately, what is happening now in our central regions is evidence of this global climate change, because we have never in our history faced such weather conditions in the past.”
Thermometer measurements show that the earth has warmed by about 1.4 degrees Fahrenheit since the Industrial Revolution, when humans began pumping enormous amounts of carbon dioxide, a heat-trapping greenhouse gas, into the atmosphere. For this January through July, average temperatures were the warmest on record, the National Oceanic and Atmospheric Administration reported Friday.
The warming has moved in fits and starts, and the cumulative increase may sound modest. But it is an average over the entire planet, representing an immense amount of added heat, and is only the beginning of a trend that most experts believe will worsen substantially.
Even Nashville’s Katrina, which was severely underreported by the major media, makes the NYT story (see “Stunning NOAA map of Tennessee’s 1000-year deluge“):
Scientists say they expect stronger storms, in winter and summer, largely because of the physical principle that warmer air can hold more water vapor.
Typically, a storm of the sort that inundated parts of Tennessee in May, dumping as much as 19 inches of rain over two days, draws moisture from an area much larger than the storm itself. With temperatures rising and more water vapor in the air, such storms can pull in more moisture and thus rain or snow more heavily than storms of old.
It will be a year or two before climate scientists publish definitive analyses of the Russian heat wave and the Pakistani floods, which might shed light on the role of climate change, if any. Some scientists suspect that they were caused or worsened by an unusual kink in the jet stream, the high-altitude flow of air that helps determine weather patterns, though that itself might be linked to climate change. Certain recent weather events were so extreme that a few scientists are shedding their traditional reluctance to ascribe specific disasters to global warming.
After a heat wave in Europe in 2003 that killed an estimated 50,000 people, the worst such catastrophe for that region in the historical record, scientists published detailed analyses suggesting that it would not have been as severe in a climate uninfluenced by greenhouse gases.
And Dr. Trenberth has published work suggesting that Hurricane Katrina dumped at least somewhat more rain on the Gulf Coast because the storm was intensified by global warming.
“It’s not the right question to ask if this storm or that storm is due to global warming, or is it natural variability,” Dr. Trenberth said. “Nowadays, there’s always an element of both.”
Kudos to the New York Times and reporter Justin Gillis for this story.
- Media wakes up to Hell and High Water: Moscow’s 1000-year heat wave and “Pakistan’s Katrina”: BBC, Reuters, USA Today, Time link warming and extreme weather; Trenberth, Stott, and Masters explain the science
- Exclusive interview — NCAR’s Trenberth on the link between global warming and extreme deluges: “I find it systematically tends to get underplayed and it often gets underplayed by my fellow scientists. Because one of the opening statements, which I’m sure you’ve probably heard is “Well you can’t attribute a single event to climate change.” But there is a systematic influence on all of these weather events now-a-days because of the fact that there is this extra water vapor lurking around in the atmosphere than there used to be say 30 years ago. It’s about a 4% extra amount, it invigorates the storms, it provides plenty of moisture for these storms and it’s unfortunate that the public is not associating these with the fact that this is one manifestation of climate change. And the prospects are that these kinds of things will only get bigger and worse in the future.”