The World Meteorological Organization made headlines in December when it released data showing that the decade winding down this month is the hottest ever recorded, and 2009 is among the 10 hottest years ever recorded.
Then why is it so cold here? North America was, in fact, cooler than average in 2009, according to the U.N. agency, and you don't need a weatherman to know that it's frigidly cold in the U.S. this week -- record-breaking cold, in some cases. So why is global warming still real, still happening and still worth doing something about?
That's the way the climate works, and it's why researchers study long-term trends more than regional blips. Southern Asia and Central Africa set new records for the hottest years on record in 2009. A little cooler than average in one spot on the globe, even one the size of North America, doesn't offset higher than average temperatures most everywhere else, and dramatically high temperatures across just as vast regions. When you average it all out, taking into account temperatures over land and sea, 2009 will rank as the fifth-warmest year recorded since 1850, according to the WMO projection. It's also among the hottest years in the last few thousand years, if you compare the data to multiple lines of evidence from ice cores, tree rings and layers of sediment, each of which offers unique but consistent clues about the past climate and the dramatic uptick we've experienced in recent decades.
Europe, the Middle East and Asia were warmer than normal, and parts of China (in addition to large swaths of Southeast Asia) set new records; overall, China experienced its third-warmest year since 1951. Heat waves sweltered in the U.K. and Italy, France, Belgium and Germany in Europe; China and India in Asia (150 died from the heat during the May heat wave in India); and Australia suffered through three heat waves (including one that spawned massive bushfires that killed more nearly 175 people) during what is likely to be the third-warmest year ever recorded there.
There's no great reason to expect that North America won't have its turn with the exceptional heat another year, as the chart to the right shows.
Droughts affected large portions of the world's population, directly and indirectly, in 2009, continuing a trend that scientists believe is exacerbated by global warming. While any one weather event can't be tied directly to global warming, scientists look for patterns and in many cases see the same results on the ground that have been predicted by computer models.
In 2009, China suffered its worst drought in five decades, and one of the weakest monsoons in the last 35 years in India left 40% of the nation suffering from drought. East African drought led to massive food shortages, central Argentina experienced severe drop damage from drought, and Australian farmers continue to struggle against a persistent drought.
North America, while wetter than many recent years (by October, areas experiencing drought were measured at their second-lowest extent this decade), the West continues to be affected by a long-term drought that threatens water supplies, farms and threatens to spawn more devastating wildfires.
The effects of global warming can be hard to describe, because you might find yourself saying at once that severe droughts will result, and that severe storms and flooding will, too. But that's the way it works: Some regions will be chronically starved of moisture, while others will see stronger deluges. Many storms will be supercharged from the extra heat in the atmosphere, so they release more water faster, causing flooding.
Case in point: Southeastern Spain had nearly a foot of rainfall over two days. In a normal year for that same spot, no more than 18 inches fall. That was the state of affairs throughout much of the Mediterranean and northern Africa this fall. Turkey experienced more rainfall in 2009 than it had in 80 years. Back in spring and summer, similar conditions were visited upon parts of Colombia, Brazil, Uruguay and Argentina. Rainfall of more than 20 inches broke monthly rainfall records in many locations. North America was not spared, either, with the northern plains of the U.S. affected by flooding in March, and the U.S. as a whole recording its wettest October in 115 years.
The poorer the country, the more damage this severe weather does. In India, severe flooding followed the weak monsoon season, killing more than 250 people. More than 1 million people were affected by September flooding in western Africa.
Arctic sea ice melted to the third-lowest extent ever recorded in September 2009, at the height of the annual melt. It would have easily set a record, except 2007 and 2008 had such dramatic melting that 2009 didn't quite set a new record. So far the annual re-freeze is not going well. Warmer-than-usual temperatures in the Arctic have sea ice extent trending along the same line as the record-breaking 2007 season.
The melting of Arctic sea ice is one of the clearest signals of global warming, and a leading indicator of what is to come. The melting is also an example -- one of many -- of a positive feedback loop that scientists expect will accelerate global warming: As sea ice melts, the darker water that is exposed absorbs more of the sun's energy, which leads to warmer waters and more melting ice.
The Arctic is referred to as the "Earth's air conditioner," moderating climate worldwide. More directly, Arctic species like polar bears, seals and walruses are becoming threatened as their habitat shrinks.
So if the Arctic begins to look more like Canada, and Canada more like the U.S., then the U.S. will look like ... some kind of Lou Dobbs nightmare.
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