A remarkably wide majority of scientists agree that global warming is happening and that human activities are the main cause. Scientists are able to make such a determination based on sound data and projections as well as careful study of the interaction between climate factors.
The Earth is a complex system where changes in one area can affect the rest of the planet, for better or worse. Climate change focuses on the overall state of the Earth’s atmosphere, ocean and land. This includes temperature, moisture levels and extreme weather events like hurricanes, droughts and wildfires.
Over the past several centuries, humanity has dramatically changed the Earth’s atmosphere by releasing large amounts of heat-trapping gases known as greenhouse gases. In particular, burning fossil fuels like coal and oil has rapidly increased the concentration of these gases.
Those gases act much like the glass in a greenhouse, trapping solar radiation and slowing its loss to space. The five key greenhouse gases include carbon dioxide, methane, nitrous oxide, chlorofluorocarbons and water vapor. All of these are caused by humans and are contributing to the increase in temperature over time.
The current level of global warming is unprecedented in the history of the Earth. The average surface temperature of the planet is about 1.2 degrees F warmer than it was in the late 1800’s and is about 0.8 degrees F warmer than the historical record over the past 100,000 years. The last decade has been the warmest ever recorded. The next two decades are expected to be even warmer.
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