Chapter 11, Image 14

Caption

Over hundreds of years. Around AD 1000, Earth was nearly as warm as it is now. After that, temperatures over much of the planet cooled by around 0.2°–0.5°C (0.4°–0.8°F), mostly during the period known as the Little Ice Age, from the 1400s to the mid-1800s. The global average has since rebounded by roughly 1°C (1.8°F) as human-produced greenhouse gases have increased. According to the 2013 IPCC report, further warming this century could run anywhere from 0.3° to 4.8°C (0.5°–8.6°F), depending on the rate of emissions. Further warming after 2100 could be substantial if greenhouse emissions continue to increase through this century, and the delayed response of ice sheets and deep oceans to warming could produce major sea level rise over several centuries.