In the early 1990s, just a few years after Jim Hansen’s 1988 testimony to Congress alerting the US and the world that climate change is here and we only have a few years to act, we were pulling ice cores out of the Greenland Ice Sheet: 3,000 meters in all, 6 meters at a time. What we learned there has formed an important cornerstone of our understanding of Earth’s climate and yielded predictions that time has confirmed.
Among our discoveries was that Earth’s climate can change rapidly. One illustrative event, among many, is from the end of the last ice age, about 12,000 years ago, when Northern Hemisphere climate “jumped” in under 5 years from ice-age, glacier-building cold and windy, to the raspberry-and-rosemary-growing, Civilization-building stable climate era we have enjoyed consistently ever since. (From our now pretty-good view of Earth’s recent few hundred thousand years of climate, this stability already seems remarkable. As we learn more about planets in our neck of the galaxy, and the rarity of the stable, benevolent climate in which we, and Civilization, have lived our entire lives, “remarkable” begins to seem an inadequate word. But I digress.)
Earth’s capacity for abrupt climate change has captured the imaginations of scientists and screenwriters alike. Could it happen to us? What would it be like? How will we know it is happening? What will the first signs be? While the full details are hard to know, we have known for a while that the Arctic will change more than the equatorial areas; in our sky-high-and-rising carbon dioxide world, this means dramatic heating. And, with enormous stores of methane frozen in Arctic permafrost, and methane an even more potent greenhouse gas than carbon dioxide, the potential for this Arctic heating to release that methane in a runaway feedback loop is terrifiying indeed. And, while the full details are hard know, we have known that an abrupt climate event would not be fun and would likely be somewhere between disastrous and catastrophic.
And, just as it is only possible to know that the stock market has peaked or bottomed in hindsight, we will only know we have had an abrupt climate event in our rear-view mirror. But. But with both the stock market and the climate, there are early signs that are consistent with such moments. And we seem to have just such climate signs on hand this month.
Recall that we report global average surface temperature relative to the average surface temperature from 1951 to 1980. On that scale, the average for 2015 jumped a whopping 0.19 °C from +0.68 °C to +0.87 °C. Recall also that we have been talking about trying to keep the ultimate rise under 2 °C, so a 0.19 °C jump in one year is troubling indeed; continuing at that rate would get us to +2 °C by around 2022, not 2100.
Enter February 2016. NASA just reported that The Earth’s average surface temperature for Feruary 2016 was +1.35 °C. Again: The Earth’s average surface temperature for Feruary 2016 was +1.35 °C, 0.48 °C higher than the 2015 average. And January and February of 2016 were both higher than any recorded month since 1980.
Yes, it is an El Niño year. Yes, it is only one month. Yes, we have had big jumps before. But not this big, and not at these already-elevated temperatures. And like a savvy investor, and given what we know about carbon dioxide and Earth's climate system, we would be fools indeed to not have in mind the possibility that this is what the onset of a large-scale, abrupt climate event looks like.