Arguments
Forecast: Permanently Hotter Summers in 20-60 years
Posted on 13 June 2011 by oslo
Guest post by Donna Hesterman
The tropics and much of the Northern Hemisphere are likely to experience an irreversible rise in summer temperatures within the next 20 to 60 years if atmospheric greenhouse gas concentrations continue to increase, according to a new climate study by Stanford University scientists. The results will be published later this month in the journal Climatic Change Letters.
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Noah Diffenbaugh, center fellow at the Woods Institute for the Environment |
In the study, the Stanford team concluded that many tropical regions in Africa, Asia and South America could see "the permanent emergence of unprecedented summer heat" in the next two decades. Middle latitudes of Europe, China and North America - including the United States - are likely to undergo extreme summer temperature shifts within 60 years, the researchers found.
"According to our projections, large areas of the globe are likely to warm up so quickly that, by the middle of this century, even the coolest summers will be hotter than the hottest summers of the past 50 years," said the study's lead author, Noah Diffenbaugh, an assistant professor of environmental Earth system science and fellow at the Woods Institute for the Environment at Stanford. The study is co-authored by Stanford research assistant Martin Scherer.
"When scientists talk about global warming causing more heat waves, people often ask if that means that the hottest temperatures will become 'the new normal,'" Diffenbaugh said. "That got us thinking - at what point can we expect the coolest seasonal temperatures to always be hotter than the historically highest temperatures for that season?"
Climate models, past and future
To determine the seasonal impact of global warming in coming decades, Diffenbaugh and Scherer analyzed more than 50 climate model experiments -including computer simulations of the 21st century when global greenhouse gas concentrations are expected to increase, and simulations of the 20th century that accurately "predicted" the Earth's climate during the last 50 years. The analysis revealed that many parts of the planet could experience a permanent spike in seasonal temperatures within 60 years.
"We also analyzed historical data from weather stations around the world to see if the projected emergence of unprecedented heat had already begun," Diffenbaugh said. "It turns out that when we look back in time using temperature records, we find that this extreme heat emergence is occurring now, and that climate models represent the historical patterns remarkably well."
According to both the climate model analysis and the historical weather data, the tropics are heating up the fastest. "We find that the most immediate increase in extreme seasonal heat occurs in the tropics, with up to 70 percent of seasons in the early 21st century (2010-2039) exceeding the late-20th century maximum," the authors wrote.
Tropical regions may see the most dramatic changes first, but wide swaths of North America, China and Mediterranean Europe are also likely to enter into a new heat regime by 2070, according to the study.
Large areas of the globe are likely to warm up so quickly that by mid-century the coolest summers will be hotter than the hottest summers of the past 50 years, according to a study co-authored by Center Fellow Noah Diffenbaugh.
Credit: Mark Shwartz
Environmental impact
This dramatic shift in seasonal temperatures could have severe consequences for human health, agricultural production and ecosystem productivity, Diffenbaugh said. As an example, he pointed to record heat waves in Europe in 2003 that killed 40,000 people. He also cited studies showing that projected increases in summer temperatures in the Midwestern United States could reduce the harvest of staples, such as corn and soybeans, by more than 30 percent.
Diffenbaugh was surprised to see how quickly the new, potentially destructive heat regimes are likely to emerge, given that the study was based on a relatively moderate forecast of greenhouse gas emissions in the 21st century.
"The fact that we're already seeing these changes in historical weather observations, and that they match climate model simulations so closely, increases our confidence that our projections of permanent escalations in seasonal temperatures within the next few decades are well founded," Diffenbaugh said.
The research was supported by the National Science Foundation, the Department of Energy, the National Institutes of Health and the World Bank.
Donna Hesterman is a science-writer intern at the Woods Institute for the Environment.
[DB] Both of these claims have been thoroughly researched and debunked. Any interested parties should go to:
It's a natural cycle
Did scientists predict an impending ice age in the 1970s?
[DB] We can also choose to believe the physics of greenhouse gases, which tell us (all other forcings remaining unchanged) that if we keep CO2 concentrations above 350 PPM we will never have another ice age again.
~James Hansen, Storms Of My Grandchildren, p. 229.
[DB] Link to disinformation site snipped. Advice: In the spirit of getting things correct, stick to reputable sources.
- The work of Dr. Latif and Dr. Keenlyside in Nature “does not allow one to make any inferences about anthropogenic global warming.” (Latif's own words).
- Their work has no forecasting skill after 2015. “We don’t trust our forecast beyond 2015.” (Latif's own words).
- Dr. Latif is not making any predictions about what will happen after 2015 other than that the long-term temperature warming trend driven by anthropogenic GHGs will continue and that the near-term temperature trend must catch up with the long-term trend, likely during a period of rapid warming.
Please note that last point. Dr. Latif's logic is that any oscillation is not warming or cooling the planet. It is merely moderating the observed result. A period of "non-warming" is a period of "delayed-warming." The end result is still the same. There is just internal variability that masks the actual year-by-year results. Terming this as either "cooling" or "lack of warming" are both inaccurate. At best, you might describe it as "delayed warming" or "hidden warming." In any event, it is a complete non-issue, and not worth the time that has already been spent on it (except with respect to the fact that any such periods of delayed warming are a very useful weapon in the arsenal of those who wish to nearly deny anthropogenic climate change).[DB] Please see http://www.skepticalscience.com/1934-hottest-year-on-record.htm. Also, please try to keep the tone more civil. As others have pointed out, Latif himself is on record as saying he was misrepresented. But that entire episode is off-topic here. If you wish to pursue it, then do so at the link Sphaerica provided.