Global Warming 101

From: Union of Concerned Scientists Global Warming 101 2005 Vies for Hottest Year on Record Global average surface temperatures pushed 2005 into a virtual tie with 1998 as the hottest year on record.[1] For people living in the Northern Hemisphere—most of the world's population—2005 was the hottest year on record since 1880, the earliest year for which reliable instrumental records were available worldwide. The year 2005 exceeded previous global annual average temperatures despite having weak El Niño conditions at the beginning of the year to normal conditions for the majority of the year. El Niño is a period of warmer-than-average sea surface temperatures in the east-central Pacific Ocean that influences weather conditions across much of the globe. In contrast, the record-breaking temperatures of 1998 were boosted by a particularly strong El Niño. The record heat of 2005 is part of a longer-term warming trend exacerbated by the rise of heat-trapping gases in our atmosphere that is due primarily to our burning fossil fuels and clearing forests. Nineteen of the hottest 20 years on record have occurred since 1980 (see table).