Where it was cooler or warmer in 2020 compared with the middle of the 20th century –1°C 0° +1° +2° +3° No data Where it was cooler or warmer in 2020 compared with the middle of the 20th century –1°C 0° +1° +2° +3° No data Where it was cooler or warmer in 2020 compared with the middle of the 20th century –1°C 0° +1° +2° +3° No data Where it was cooler or warmer in 2020 compared with the middle of the 20th century –1°C 0° +1° +2° +3° No data This warming is unprecedented in recent geologic history. A famous illustration, first published in 1998 and often called the hockey-stick graph, shows how temperatures remained fairly flat for centuries (the shaft of the stick) before turning sharply upward (the blade). It’s based on data from tree rings, ice cores and other natural indicators. And the basic picture, which has withstood decades of scrutiny from climate scientists and contrarians alike, shows that Earth is hotter today than it’s been in at least 1,000 years, and probably much longer. In fact, surface temperatures actually mask the true scale of climate change, because the ocean has absorbed 90 percent of the heat trapped by greenhouse gases. Measurements collected over the last six decades by oceanographic expeditions and networks of floating instruments show that every layer of the ocean is warming up. According to one study, the ocean has absorbed as much heat between 1997 and 2015 as it did in the previous 130 years. We also know that climate change is happening because we see the effects everywhere. Ice sheets and glaciers are shrinking while sea levels are rising. Arctic sea ice is disappearing. In the spring, snow melts sooner and plants flower earlier. Animals are moving to higher elevations and latitudes to find cooler conditions. And droughts,... |