Global Warming Acceleration

(GET editor’s note: We are providing the first couple of paragraphs of this article and a link to the website at Columbia University. We do want all of our readers to be aware of the conclusion, however, and so we start by quoting the article’s last paragraph:

Global temperature prognostication: 2021 will be cooler than 2020, because of the lagged effect of the current strong La Niña. When the next El Niño occurs, perhaps about mid-decade, hang onto your hat. Global emissions of GHGs had better be trending down by then!

Please understand this – it is important!)

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14 December 2020

James Hansen and Makiko Sato

Fig. 1. Global surface temperature anomalies (relative to 1880-1920) in 2016 and 2020.

Abstract. Record global temperature in 2020, despite a strong La Niña in recent months, reaffirms a global warming acceleration that is too large to be unforced noise – it implies an increased growth rate of the total global climate forcing and Earth’s energy imbalance. Growth of measured forcings (greenhouse gases plus solar irradiance) decreased during the period of increased warming, implying that atmospheric aerosols probably decreased in the past decade. There is a need for accurate aerosol measurements and improved monitoring of Earth’s energy imbalance.

November 2020 was the warmest November in the period of instrumental data, thus jumping 2020 ahead of 2016 in the 11-month averages (Fig. 1). December 2016 was relatively cool, so it is clear that 2020 will slightly edge 2016 for the warmest year, at least in the GISTEMP analysis.

The rate of global warming accelerated in the past 6-7 years (Fig. 2). The deviation of the 5-year (60 month) running mean from the linear warming rate is large and persistent; it implies an increase in the net climate forcing and Earth’s energy imbalance, which drive global warming.

Fig. 2. Global temperature and Niño3.4 Index through November 2020.

Variability of the 12-month running mean about the linear warming trend in the past 50 years is mainly unforced variability associated with ENSO (El Niño Southern Oscillation).

Read more at James Hansen’s Columbia University website.