UN: Last decade was warmest on record, but weather-related fatalities fell
The World Meteorological Organization's review of severe weather and climate 2001 to 2010 shows that nine years in that decade were among the 10 warmest on record. Even normally cool La Niña years warmed up.
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Indeed, as if to underscore the influence of climate change on natural variability, each La Niña but one since the mid-1970s has been warmer than the previous La Niña event. This coincided with a marked increase in global average temperatures.Skip to next paragraph
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The 2001-10 decade also has seen a slight cooling trend that has continued. Some political skeptics of global warming have cited this as evidence that global warming is over. Climate scientists are puzzling over the trend as well.
Global temperature records compiled at centers in the US and Britain show a similar ramp-up in temperatures from 1910 to the late '40s or early '50s, only to see a slight cooling trend that continued into the mid-to-late '70s, before global average temperatures resumed their increase.
Researchers have been hunting for the "missing heat." Some suggest that some of the heat has been taken up through melting polar and glacial ice. Others have pointed to reflective aerosol particles that likely increased with the coal-fired economic explosions in China and India over the past decade.
Still others are looking to the deep ocean as a repository for the missing heat. A team of scientists in the US and Britain published an analysis in May of ocean-temperature data during the decade. They conclude that a significant amount of the missing heat has gone into the deep ocean, below 700 meters. The work appeared May 23 in the journal Geophysical Research Letters.
Whatever the reason for the slight throttling back of temperature increases, temperatures remained significantly above the 1961-'90 base period the WMO uses for its data. And warming has remained significant enough to load the dice for the severe weather and climate events recorded during the decade, researchers say.
Citing data from NOAA, the WMO notes that the 2001-10 decade was the most active for Atlantic tropical cyclones since 1855, although in other regions, tropical-cyclone activity was near or below normal.
Since 1901, only the '50s was a wetter decade globally – significantly so. Even so, 2010 was the wettest year on record, globally.
Over the decade, the proportion of countries reporting record maximum temperatures has grown, while the proportion of countries reporting record lows has declined – anchoring a trend that has been building since the 1960s.
One of the most dramatic signs of change has come in the Arctic, which has seen an erratic but long-term decline in extent and thickness of summer sea ice – a crucial component of the global and regional climate system. In 2007, the extent reached a record low, some 39 percent below the long-term average. That record was eclipsed last year. Greenland's ice sheet and key regions of Antarctica's continental ice sheet also have been losing mass. The decade's largest declines in mass were seen in 2007 and '08, the WMO says, adding to sea-level rise already under way because of ocean warming.
The WMO acknowledges that while it's not yet possible to tie a specific storm or even heat wave directly to global warming, climate scientists "increasingly conclude that many recent events would have occurred in a different way – or would not have occurred at all – in the absence of climate change."