Two Plus Two Equals = You Really Don't Want to Know.

Let's do the math.  Since the beginning of the Industrial Revolution our greenhouse gas emissions have warmed the atmosphere by 0.8 degrees Celsius. Emissions to date, even if we turned emissions-free tomorrow, have already locked in 1.5 degrees Celsius of warming by 2100.  Our leaders have designated 2 degrees Celsius as the "never exceed" point if we're to have a better than even chance of avoiding runaway global warming, i.e. a major extinction event.

So, how are we doing?  Lousy.

The latest research concludes that it's going to get a lot hotter and lot faster over the next few decades.  How much?  About 0.25 degrees Celsius each and every decade.

For the record, the Industrial Revolution is generally thought to have begun around 1790.  In other words, in two and a quarter centuries we've seen warming of 0.8 degrees Celsius.  Soon we'll be seeing that much warming again over the span of just three decades.  That's not good, not good at all.

The Pacific Northwest National Laboratory (PNNL) study, “Near-term acceleration in the rate of temperature change,” finds that by 2020, human-caused warming will move the Earth’s climate system “into a regime in terms of multi-decadal rates of change that are unprecedented for at least the past 1,000 years.”

In the best-case scenario PNNL modeled, with atmospheric carbon dioxide concentrations stabilizing at about 525 parts per million (theRCP4.5 scenario), the four-decade warming trend hits 0.45°F (0.25°C) per decade. That means over a 4-decade period, the Earth would warm 1.8°F (4 x 0.45) or 1°C (4 x 0.25). This is a faster multi-decadal rate than the Earth has seen in at least a millennium.

Because of Arctic amplification, the most northern latitudes warm two times faster (or more) than the globe as a whole does. As this figure from the study shows, the rate of warming for the Arctic is projected to quickly exceed 1.0°F (0.55°C) per decade.

Such rapid Arctic warming would be ominous for several reasons. First, it would likely speed up the already staggering rate of loss of Arctic sea ice. Second, if, as considerable recent research suggests, Arctic amplification has already contributed to the recent jump in extreme weather, then the next few decades are going to be utterly off the charts.

Third, such rapid Arctic warming implies that the rapidly-melting Greenland ice sheet — already made unstable by human-caused warming — is likely to start disintegrating even faster, which in turn will push sea level rise higher than previously estimated, upwards of six feet this century.

Fourth, such rapid warming would serve to accelerate the release of vast amounts of carbon from defrosting permafrost — the dangerous amplifying carbon cycle which has already been projected to add up to 1.5°F to total global warming by 2100.

This sounds an awful lot like that 'runaway global warming' mom warned us about. 2020.  Hmmm, not very far off, is it.