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Earth is a dynamic sphere and, it turns out, so is the planet's climate, otherwise known as the long-term trend of global weather conditions. It's no wonder questions and myths abound about what exactly is going on in the atmosphere, in the oceans and on land. How can we tell our orb is actually warming and whether humans are to blame? Here's a look at what scientists know and don't know about some seemingly murky statements on Earth's climate. [50 Amazing Facts About Earth]
Climate has changed beforeSlide 2 of 21
Climate has changed before
Myth: Even before SUVs and other greenhouse-gas spewing technologies, Earth's climate was changing, so humans can't be responsible for today's global warming.
Science: Climate changes in the past suggest that our climate reacts to energy input and output, such that if the planet accumulates more heat than it gives off global temperatures will rise. It's the driver of this heat imbalance that differs.
Currently, CO2 is imposing an energy imbalance due to the enhanced greenhouse effect. Past climate change actually provides evidence for our climate's sensitivity to CO2.
(Image left: heat given off by Earth's surface and atmosphere; Right: sunlight reflected back out to space.)Slide 3 of 21
... but it's cold outside!Slide 4 of 21
... but it's cold outside!
Myth: The planet can't be warming when my front yard is covered in several feet of snow. … This winter has been one of the chilliest, how is that possible in a warming world?
Science: Local temperatures taken as individual data points have nothing to do with the long-term trend of global warming. These local ups and downs in weather and temperature can hide a slower-moving uptick in long-term climate. To get a real bead on global warming, scientists rely on changes in weather over a long period of time. To find climate trends you need to look at how weather is changing over a longer time span. Looking at high and low temperature data from recent decades shows that new record highs occur nearly twice as often as new record lows.
For instance, a study published in the journal Geophysical Research Letters in 2009, found that daily record high temperatures occurred twice as often as record lows over the prior decade across the continental United States.Slide 5 of 21
Climate is coolingSlide 6 of 21
Climate is cooling
Myth: Global warming has stopped and the Earth has begun to cool.
Science: The last decade, 2000-2009, was the hottest on record, according to Skeptical Science. Big blizzards and abnormally chilly weather often raise the question: How can global warming be occurring when it's snowing outside? Global warming is compatible with chilled weather. "For climate change, it is the long-term trends that are important; measured over decades or more, and those long term trends show that the globe is still, unfortunately, warming," according to Skeptical Science.Slide 7 of 21
The sun is to blameSlide 8 of 21