When determining which year was the hottest year, care should be taken to avoid bias due to temporary conditions such as the El Niño that was present in 2016 and the La Niña we're now experiencing now. Above image uses NASA land+ocean January 2012-December 2017 anomalies from 1951-1980, adjusted by 0.59°C to cater for the rise from preindustrial to 1951-1980, to calculate a linear trend that goes some way to smooth out variability due to El Niño/La Niña events. The trend shows that 2017 was significantly warmer than 2016.
The trend also shows that 1.5°C above preindustrial was crossed back in 2016. This 1.5°C (or 2.7°F) was set at the Paris Agreement as a guardrail that was not to be crossed. The trend further shows that we've meanwhile crossed 1.6°C above preindustrial and we look set to cross the 2°C guardrail within years.
Global warming has crossed 1.5°C / 2.7°F above preindustrial and looks set to cross 2°C / 3.6°F soon. Due to accelerating warming in the Arctic, that could happen within one or two years time, i.e. much faster than the trendlines below may suggest.
Indeed, warming in the Arctic is taking place much faster than elsewhere, and the difference is accelerating. There's a huge danger that accelerating warming in the Arctic will speed up feedbacks such as:
• huge amounts of methane getting released from the seafloor of the Arctic Ocean;
• melting of sea ice and permafrost causing more sunlight to get absorbed in the Arctic, as less sunlight gets reflected back into space;
• changes to jet streams causing more extreme weather, in turn resulting in more emissions, such as due to wildfires;
• and more.
As said, such feedbacks could speed up global warming much more than above trendlines may suggest.
Add up the impact of all warming elements and, as an earlier analysis shows, the rise in mean global temperatures from preindustrial could be more than 10°C in a matter of years, as illustrated by above image.
|[ Danger Assessment, from earlier post ]|
• Climate Plan
• Warming is accelerating
• The Arctic is changing the Jet Stream - Why This Is Important
• 10°C or 18°F warmer by 2021?
• Abrupt Warming - How Much And How Fast?
• Methane Erupting From Arctic Ocean Seafloor
• Warning of mass extinction of species, including humans, within one decade