Measurements of the concentration of carbon dioxide since 1959 (316 ppm) have revealed an increase to 387 ppm in 2009, or at an average 1.42 ppm per year.
The global average surface temperature fluctuates over time, but recently it has increased dramatically. From 1920 to the present, the Earth’s average surface temperature has increased by around 1.4 °F. The current warming trend is proceeding at a rate that is unprecedented in at least the past 1,300 years.
A study released by the U.S. National Academy of Sciences in 2010 said, “Climate change is occurring, is caused largely by human activities, and poses significant risks for — and in many cases is already affecting — a broad range of human and natural systems.”
Recent disease outbreaks are consistent with model projections that warmer, wetter conditions will lead to greater transmission potential at higher altitudes and elevations.
Human activity is causing the Earth to get warmer.
Sea levels have risen approximately 1 inch. At the current rate, scientists predict that it will have devastating effects by the year 2100.
Since 1990, yearly emissions of carbon dioxide have gone up by about 6 billion metric tons worldwide, which is more than a 20% increase. Almost all of that increase is due to human activities.
In the past few decades, temperatures in the Arctic have risen at nearly twice the rate as in the rest of the world, disrupting the region and its people in many ways.
And, because they can do a much better job of explaining the difference between “climate” and “weather”, from the Union of Concerned Scientists:
Climate is a good indicator of what to expect in general, such as cold days in February in New England. Weather, on the other hand, is what we actually experience, like a blustery, snowy day with temperatures in the low 20s. In other words, climate describes phenomena observed over long time periods, such as decades and centuries, while weather is observed over short time periods, such as days and weeks.
It is clear that the Earth’s climate is changing, largely due to human activity. Over the last 25 years, Earth’s global average temperature has been increasing at more than twice the rate of the last century. In fact, nine of the warmest years on record have occurred in just the last 10 years.,  This warming has been accompanied by a decrease in very cold days and nights and an increase in extremely hot days and warm nights. Additionally, the oceans reached their highest recorded temperature in the summer of 2009. Oceans have absorbed much more heat from global warming than the air at the Earth’s surface because water is much better at retaining heat.
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