03 August 2010

Past Decade Warmest Ever Recorded, Scientists from 48 Nations Say

Report shows human society faces consistently warmer climate conditions

By Cheryl Pellerin
Science Writer

Washington ― Earth has been warming for 50 years and the past decade was the warmest ever recorded, according to more than 300 scientists in 48 countries who contributed to the 2009 State of the Climate report released July 28.

The data are historical, not theoretical. The data come from weather stations, satellites, weather balloons, ships and ocean buoys all over the world. Scientists used the data to study 37 different indicators of global temperature change with a focus on 10 that are most directly related to surface temperatures.

According to the report, seven of the indicators are rising: air temperature over land, sea-surface temperature, air temperature over oceans, sea level, ocean heat, humidity and temperature in the troposphere, the layer of the atmosphere nearest the surface where weather occurs. Three are falling: Arctic sea ice, glaciers and spring snow cover in the Northern Hemisphere.

Human society has developed for thousands of years under one climatic state, the report says, and now a new set of climatic conditions is taking shape.

“The instrumentation goes from the top of the atmosphere to several thousand meters deep in the ocean,” said Deke Arndt, co-editor of the report and chief of the National Climatic Data Center’s Climate Monitoring Branch at the U.S. National Oceanic and Atmospheric Administration (NOAA).

“The evidence for warming is very widespread,” Arndt told America.gov. “In the science arena it’s not controversial at all ― it’s really apparent that all of these things are being driven by a common factor and that common factor is that the planet is getting warmer.”

NOAA produced the report with editorial leadership from the United States, the United Kingdom, Canada and Australia and technical contributions from 160 research groups worldwide. State of the Climate was published as a special supplement to the Bulletin of the American Meteorological Society and was edited by Arndt, M.O. Baringer and M.R. Johnson of NOAA.

REGIONAL CLIMATES

In 2009, large areas of South America, southern Asia, Australia and New Zealand experienced extreme warmth and the United Kingdom, China and the Russian Federation reported severe cold snaps.

Large parts of southern North America, the Caribbean, South America and Asia experienced drought, and heavy rainfall and floods affected Canada, the United States, Amazonia and southern South America, many countries along the east and west coasts of Africa and the United Kingdom.

Extreme weather events around the world included the following:

• In Brazil, extreme rainfall in the Amazon basin caused the worst flood in a century; 40 people were killed and 376,000 left homeless.

• In northwest England, heavy rainfall flooded the Lake District, setting new records for river flows and damaging 1,500 properties.

• Three heat waves broke temperature records in Australia. One was accompanied by high winds that fanned brush fires, killing 173 people.

• In southeastern South America, the wettest November in 30 years displaced thousands of people.

• In northern Iberia and southern France, a North Atlantic storm raked the land with record winds, downed power lines, closed airports and blocked railroads.

• The central north Pacific, which includes Hawaii, experienced several tropical cyclones after years of relative calm.

“We get extreme events every year,” Arndt said. “We can’t really say climate change caused item number three in that list, but what we can say is that climate science would expect higher-magnitude events to occur more often. In the United States, where we thankfully have the data to study these things, we are seeing more extreme events happen more often.”

WARMING OCEANS

According to the report, more than 90 percent of the warming that’s happened on Earth during the past 50 years has gone into the oceans, and new studies show that the world’s oceans are heating up as they absorb most of the extra heat being added to the climate system from the build-up of heat-trapping greenhouse gases.

Warming has been observed as far as 6,000 feet (1,829 meters) below the surface, the report says, but most of the heat is accumulating in the oceans’ layers near the surface.

“It’s becoming more and more apparent that the ocean is a huge reservoir for heat and energy,” Arndt said. “The question is when does its carrying capacity run out. There’s a big flurry of research in that arena.”

Water expands as it warms, and ocean heating is responsible for much of the world’s sea-level rise, the report says. Melting of land-based ice is responsible for the rest. Because they warm and cool much more slowly than air, the oceans will hold on longer to the heat they’ve accumulated.

“If you warm the ocean it’s going to have an impact on living things that depend on the ocean, and for landlubbers the ocean is connected to the atmosphere,” Arndt said.

“If you warm the ocean, you warm the atmosphere and encourage a lot more evaporation so that moisture feeds back into the system, and we likely see that as bigger precipitation events,” he added. “So what happens in the ocean doesn’t stay in the ocean — the connection with a lot of other pieces of the climate system is water.”

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(This is a product of the Bureau of International Information Programs, U.S. Department of State. Web site: http://www.america.gov)