Freedman: Global Warming Has Not Been Canceled
Many stories were written last week about a study in the scientific journal Nature [subscription required] showing that, during the next few years, naturally shifting ocean currents may offset some of the greenhouse gas-induced warming trend for parts of North America and Europe. The trouble with the study was that its many gray areas were lost in the black and white world of climate change discourse in the United States.
"Global Warming Will Stop," blared the typically shrill headline of the latest 'contrarian-gram' press release from Oklahoma Republican Senator James Inhofe's office.
Sorry senator, but the study did not show that global warming has been canceled. At the most it showed that further significant increases in global temperatures might be slightly postponed until after about 2015, or potentially earlier, by natural climate trends.
The study by a group of European climate researchers, led by Noel Keenlyside of the Leibniz Institute of Marine Sciences in Germany, was based on preliminary results from a new method that uses computer models to generate shorter-term (decadal) climate predictions based on real world oceanic and atmospheric conditions. Keenlyside and his co-authors fed recent ocean surface temperature data into the models to produce their results.
As Joseph Romm pointed out on ClimateProgress, the study used a decadal timescale in a way that was easily misinterpreted by many journalists and rabble-rousers such as Inhofe. The study compared the mean temperature during the period between 2005 and 2015 with the mean temperature of the period between 2000 and 2010. That's not the same as saying that the next ten years, from 2008 to 2018, are going to be colder than normal in North America and Europe, which is how some reported the story. Romm wrote that the study's conclusion is actually consistent with other studies that have shown that rapid warming may commence again sometime soon after 2010.
The recent Nature study demonstrates that manmade, or anthropogenic, climate change needs to be viewed in its proper context. Too often it seems that there is scant room within the competing popular paradigms on climate change to convey the reality that global climate change doesn't mean that the climate will warm significantly, or even at all, every single year.
As National Center for Atmospheric Research climate scientist Kevin Trenberth succinctly put it to Andrew Revkin in the May 1 edition of the New York Times, "Too many think global warming means monotonic relentless warming everywhere year after year."
"It does not happen that way."
This is a key point that has not penetrated far into the public's (or the media's) conscience.
Global warming is taking place in fits and starts, with an overall upward trend in temperatures amidst the background noise of significant year-to-year variations. What the recent study did was try to clarify some of this background noise.
It's because of the natural climate variability that I cringe every time I see someone in the environmental community or in journalism try to link a single severe weather event to climate change, such as Hurricane Katrina. I worry that support for taking action to reduce greenhouse gas emissions is thereby being built on the shoddy foundation of weather variability, rather than on the messier but more significant long-term record of climate change.
Take a look at any graph of temperature trends over the past 100 years and you'll see the tug of war between natural climate variability and manmade climate change caused by increasing atmospheric concentrations of greenhouse gases such as carbon dioxide. The overall temperature trend is clearly one of warming, but some years are colder than the year before it.
But if such a cooling trend came to pass, would the momentum for climate change action, which is based upon ever increasing temperatures, be sustainable? As Revkin asked in a piece on his "Dot Earth" blog on May 1: "Can Climate Campaigns Withstand a Cooling Test?"
The answer, in my view, is that climate campaigns would not be sustainable if they are built around a simplistic view of climate change that holds that the world will be warmer with each passing day, week, month, and year. The answer is yes if scientists, policymakers, and journalists succeed in moving the debate to its proper context within the broader issues of contemporary global challenges, such as energy security and population growth.
Keep in mind that even if the Nature study had shown that Londoners and New Yorkers will be shivering throughout the next decade, it would not have necessarily negated the scientific consensus pointing to long-term warming due to human activities. Still, judging from the confusion that greeted the study this week, I doubt that an actual prolonged cold period would be treated as anything other than the collapse of the scientific consensus on climate change.
Revkin's question reminded me of the fact that in 1988, former Senator Timothy Wirth of Colorado and his colleagues deliberately scheduled the first major hearings on global warming on one of the statistically hottest days of the year in Washington, and then had aides turn off the air conditioning in the hearing room for added effect. That human interference with the indoor climate demonstrated that people, and poll-driven politicians in particular, respond to the weather and the climate that they feel, not the atmosphere that they see projected years into the future. If warming were to halt for a decade, it's entirely possible that momentum to reduce greenhouse gas emissions would come to a standstill as well, even though from a scientific perspective it should do no such thing.
I invite you to share your thoughts about how a few years without significant warming might affect climate change mitigation and adaptation efforts. Will there be fewer incentives to act? Do you feel that the media, environmentalists, and politicians are clearly conveying the distinction between natural variability and human influences on the climate system?
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