That's a Wrap: Humans-Caused The Hottest Decade on Record

2019 was the second hottest year on record, capping off the hottest decade on record

Humans have caused 100 percent of observed warming since the 1950s. The science is unequivocal. The latest UN global assessment report identified humans as the cause of at least 100 percent of observed warming (IPCC Synthesis Report, 2014). The Fourth US National Climate Assessment also found that​​​ the likely human contribution for the 1951–2010 change to be 93 to 123 percent (USGCRP, 2017; Wigley and Santer, 2012). A contribution of greater than 100 percent indicates that some natural forces, such as volcanoes, are working to cool the Earth, but are being overwhelmed by the effects of greenhouse gases.

Humans-caused warming is breaking all kinds of temperature records, underscoring the accelerating rate of climate change and the increase in major impacts – such as sea level rise, ice loss and extreme weather. These days, temperature records don't last long and often smash their way into hotter territory. 2010 was the hottest year on record. Then, 2014 and every year since topped the record set in 2010. The 2010s saw 17 of the 20 hottest months on record. July 2019 tied 2016 as the hottest month on record. The Earth reached the highest temperature on record – 129.2°F (54°C) – twice: first in Death Valley, California on June 20, 2013 then again in Mitribah Kuwait on July 21, 2016.

Climate change is directly responsible for many heat records. Human-caused climate change has contributed to the severity and probability of 82 percent of record-hot days globally (Diffenbaugh et al. 2017). The Northern hemisphere’s extreme heatwave in 2018 was ‘impossible’ without climate change (Vogel et al. 2019). As for annual temperature records, the global heat record in 2016 could not have happened but for climate change (Knutson et al. 2018). Climate change is also responsible for marine warming in the Gulf of Alaska and the Bering Sea from 2014–16 (Walsh et al. 2018).

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