Soot and methane cuts promise threefold benefits

Vehicles are a significant source of black carbon and other pollutants in many countries. Credit: Caramel/flickr

Limiting methane and soot emissions would save lives and keep farming output high, as well as playing an important role in fighting global warming. That’s according to some 70 scientists who have reviewed the available research on these substances for the United Nations Environment Partnership (UNEP). Such cuts were also surprisingly feasible, with just 16 ways of limiting emissions providing about 90 percent of the possible climate benefit from a list of 2000 control measures.

“We estimate that adoption of the 16 control measures we considered would save about 2 million lives a year and save 50 million tons of crops a year,” said NASA’s Drew Shindell, who led the project. “For climate, putting control measures in place could eliminate about half the warming we’ll otherwise face over the next 40 years.”

Evidence of humans’ role in deluges starts to flow

Flooding in York, UK, in Autumn 2000. Credit: Gordon Hatton

Human greenhouse gas emissions made heavy rain and snowfall and local flooding more likely, scientists have shown this week. On Thursday top scientific journal Nature published two separate papers that are among the first to show that humans are contributing to the deluges that affect us.

Although global warming has previously been associated with more heavy rainfall, a lack of daily observations mean that prior studies have mainly relied on comparing different climate models. By contrast, Francis Zwiers of government ministry Environment Canada and University of Victoria, and colleagues instead compare observed and simulated changes. They looked at extreme rain and other wet weather brought together under the general grouping “precipitation”. Using data from 6,000 weather stations collected by the Hadley Centre of the UK’s Met Office, they looked at the highest daily and five-day consecutive precipitation amounts in any given year from 1951-1999.

“The work that we did was to examine how annual precipitation extremes change over Northern hemispheric land areas,” Zwiers told a press conference on Wednesday. “We see, as many others have done, that these events intensified over the latter half of the 20^th century.” Zwiers and co-workers from Canada and Scotland also found that there is a pattern of change in the observed data that matches those seen in models simulating greenhouse-gas driven global warming.

Atlantic cold tongue tells of humans’ climate impact

Wind waves depend on wind speed and have long been logged by ship crews. Ocean wind data corrected with wind-wave heights suggests a slow down of the southeast trade winds in the equatorial Atlantic. Credit: Image courtesy of Ship DAVID STARR JORDAN, NOAA Photo Library.

Humanity has significantly altered the climate in the tropical Atlantic between 1950 and 2009, gradually weakening the area’s trade winds, University of Hawaii at Manoa researchers say. That effect is caused by burning fossil fuels, Hiroki Tokinaga and Shang-Ping Xie explain. However, it is more directly driven by the aerosols of soot and sulfur-based particles this releases than global warming caused by the resulting CO2 greenhouse gas emissions.

Falls in aerosol emissions now look set to reverse this trend, Tokinaga notes, showing how government actions can influence the environment. “Human-produced aerosol emissions had continuously increased until the 1970s, but then they started to decrease because of legislation in North America and Europe,” he told Simple Climate. “Increased greenhouse gas forcing contributes to a broader warming of the tropical Atlantic. Another climate shift might happen when the increased greenhouse gas forcing gets stronger than the aerosol forcing in the next few decades.”

Climate researchers warn of food and forest tinderbox

In January, food prices reached their highest levels since the UN Food and Agricultural Organisation began monitoring them in 1990. Credit: UN Food and Agricultural Organisation.

More frequent droughts are set to pose challenges to food supplies, and could worsen global warming still further. That’s a message that’s emerged over the past week, which has seen world food prices reach record highs, while researchers unveiled stark messages about drought in Africa and the Amazon forest.

Eastern Africa is seeing decreased rainfall due to warming in the Indian Ocean warn University of California, Santa Barbara, scientists Chris Funk and Park Williams. Over the past 60 years the Indian Ocean has warmed two to three times faster than the central tropical Pacific, they note in a paper published in the journal Climate Dynamics online ahead of print. This has driven increased rain and cycling of air through the atmosphere in the tropical Indian Ocean region. This has extended part of the air flow system known as the Walker circulation westwards, sending dry air towards eastern Africa.