Either global warming is the greatest crisis ever to confront humankind, or it is a lefty plot completely manufactured by scientists and politicians in pursuit of research funding and control over our lives. That's about the way it plays out in the media, on blogs and in conversations on the Metro. Anyone out front on this issue is either an apocalyptic or a denier, virtuous or vile.
Similarly, one camp maintains that temperatures are rising dramatically with unspeakable portents, while the other thinks what has happened is entirely a result of undefined internal oscillations in the earth-sun climate system, and that there is virtually no human component to climate change. This group is especially fond of the lack of statistically significant surface warming since 1995. Since 1997, temperatures really flatlined.
There's a third way, which suffers from the problem that it is subtle, neither black nor white, and doesn't do well in sound bites. It's a "lukewarm" synthesis, arguing indeed that humans have something to do with the rise in surface temperature measured since the mid-1970s, but that it is hardly the end of the world as we know it. This view claims to accommodate the seemingly odd behavior of temperature in the last 15 years.
Each of these positions — let's call them hothead, flatline, and lukewarm — are testable against observed history and theory. To keep some interest in this occasionally boring topic, I'm going to examine them sequentially, starting with the hotheads.
The hothead argument is that we have already set the planet on the road to climate calamity, and that we must promptly reduce the atmospheric concentration of dreaded carbon dioxide- the main global warming emission — to levels seen decades ago.
Before we started torching carbon stored in forests and then carbon stored underground as coal and oil, the carbon dioxide concentration of our atmosphere was about 280 parts per million (ppm). It's now around 390, and headed for a nominal doubling to 600ppm between 2070 and 2090 if the world continues its current rate of development and does not find an effective (meaning neither solar nor wind) and politically acceptable (meaning not nuclear, at least for now) alternative for hydrocarbon fuels.
The high priest of the hotheads is NASA's James Hansen, who preaches that, unless we dial back to 350ppm, we will lose, within a hundred years' time, the vast majority of Greenland's ice, which will raise sea levels about 20 feet. Hansen has testified that he thinks this could happen within a hundred years.
The hothead theory is that the ice on that gigantic island is much less stable than previously thought, and that with a tad more warming, lakes will form in the summer, drain thousands of feet down to the bedrock, and lubricate the flow to the ocean. It quickly melts, submerging a lot of Florida and Manhattan. The Washington Monument becomes an island.
The reason that glaciers flow to begin with is because the bottom is liquid. It's quite unclear that simply adding more water will have much effect. Recent studies indicate that when the lakes drain suddenly into the ice, the acceleration of flow is not sustained. But that's today; what about in the future?
One way to project the future with confidence is to look to history, when it was warmer. Danish colonists established a series of weather stations on the Greenland coast, with reliable records that go back over 225 years. They unequivocally show that — from 1920 through 1960 — there was substantially more warming than has been observed in recent decades. If hothead theory is correct, there should have been a detectable jump in sea level during that period, but there was none.
Further, there is very strong evidence that the integrated warming — that's temperature times time — was much greater for millennia after the end of the recent ice age around 10,800 years ago. Assuming that humans will find something better to power the world with than carbon dioxide-emitting fossil fuels in the next one or two hundred years, that total warming back then was greater or equal to what we are likely toinflict on Greenland.
In those millennia — which are only the blink of a geologist's eye ago — trees used to grow where there is now only barren tundra. When they died, they were preserved in the acidic bogginess, so we can tell exactly when they were alive with carbon dating. It's very clear that the forest in Eurasia used to extend all the way to the Arctic Ocean during that warm period.
Plant ecologists know that the northern limit of the forest is determined by the mean July temperature. The dead trees tell us it was as much as 13 degrees F warmer than the 20th century average.
The author of that work, Glen MacDonald of UCLA, has noted that the only way to get that region so warm is with a massive influx of Gulf Stream water from the Atlantic. The only "gate" for that is the channel between Greenland and Scandinavia, which means that Greenland (at least the eastern half) would have been pretty balmy compared to today.
And Greenland still retained the lion's share of its ice cap.
Even so, the Arctic Ocean was likely to have been largely ice-free during the summer during much this time — from 6,000 to 8,000 years ago — as noted by theUniversity of Stockholm's Martin Jacobsson in a 2010 edition of the scientific journal Quaternary Science Reviews. The Geological Survey of Norway foundsomething similarin 2008. Not only did Greenland's ice survive — so did the polar bear.
So it appears that the ice that the hotheads skate on is pretty thin. Are the flatliners doing any better? We'll have a look in Part 2.