Can Global Warming Cause an Ice Age?

Though some parts of the country have been hammered by powerful storms and roasted by hellish heat waves, climate change skeptics insist that this is just normal variation and not proof of global warming. But a year and a half ago many of those same skeptics were saying that the extensive snowfalls that hit the northeast "proved" that climate change was a hoax, and that we were really on the brink of an ice age. Why is one snowy winter sufficient to disprove climate change, while a 100-year trend of ever-increasing average temperatures no proof at all?

Other articles, like this one from Pravda, claim that theories of Anthropegenic Global Warming ignore long-term historical trends and that we're really entering another ice age. The article insists that humans aren't generating the increased CO2 levels, but rather natural warming is causing CO2 levels to rise. The mechanism they propose is potentially reasonable for previous ice age cycles, but this time it's different: this time seven billion people are pumping megatons of CO2 into the air every day. CO2 levels are increasing much faster than the historical norms they're referencing.

It's interesting that the Koch brothers and the Communist propaganda organ Pravda are on the same side of the climate debate. Could it have anything to do with the fact that Russia is one of the world's biggest oil exporters?

Forecasting climate change is complex and difficult science. But predictions that NASA scientist James Hansen made 20 years ago in an article in Science are proving to be true. From the article's abstract:

Summary. The global temperature rose by 0.20C between the middle 1960's and 1980, yielding a warming of 0.4°C in the past century. This temperature increase is consistent with the calculated greenhouse effect due to measured increases of atmospheric carbon dioxide. Variations of volcanic aerosols and possibly solar luminosity appear to be primary causes of observed fluctuations about the mean trend of increasing temperature. It is shown that the anthropogenic carbon dioxide warming should emerge from the noise level of natural climate variability by the end of the century, and there is a high probability of warming in the 1980's. Potential effects on climate in the 21st century include the creation of drought-prone regions in North America and central Asia as part of a shifting of climatic zones, erosion of the West Antarctic ice sheet with a consequent worldwide rise in sea level, and opening of the fabled Northwest Passage.

We are seeing all of these effects, just 20 years on.

The funny thing about the climate change skeptics' claims that we're entering an ice age is that scientists have long feared global warming could cause an ice age. The reason is that a current along the American east cost, the Atlantic Conveyor, brings warm water up from the south Atlantic to Europe: this is why western Europe has much warmer winters than land-locked Russia.

The melting of the Greenland ice sheet could bring a flood of fresh water into the north Atlantic, deflecting the Atlantic Conveyor away from Europe. A colder Europe would have more snow cover, reflecting more light back into space, cooling the planet, allowing more snow to fall in North America, which would cool the planet even more and potentially cause an ice age.

I have to admit the Atlantic Conveyor seems rather esoteric. Hansen's paper, however, brings up a different scenario when he mentions volcanic aerosols. It's well known that massive volcanic eruptions can cause world-wide cold snaps. The 1883 eruption of Krakatoa cooled temperatures globally by 1.2 C for five years. The eruption of Mount Pinatubo in 1991 cooled the earth by one-half to one degree Celsius. The Little Ice Age may have been caused by volcanoes. And the Bubonic Plague may have been caused by volcanic eruption in 535.

Now there's a lot of water locked up safely in the polar ice caps. When they melt that water will go into the sea, causing sea levels to rise, and into the air, as water vapor.

If a large volcanic eruption such as Krakotoa were to occur during the Northern Hemisphere winter, temperatures would cool drastically. The water that global warming had freed from the ice caps at the poles could then precipitate out as snow over the entire Northern Hemisphere. This would reflect sunlight back into space, cooling the earth and amplifying the effects of the volcanic aerosols. This could mean years with no summer and no growing season.

Each year of the cold snap caused by the volcano more and more of the snow would stay, and the earth would grow cooler. After the the effects of the volcano wore off it would be too late: the northern hemisphere would be locked in permanent winter, for thousands of years.

If all that water had still been locked in the poles, the area of the volcano-caused snow cover would be inherently limited, and an ice age would be less likely. But since global warming allowed the water in polar ice to migrate across the planet, all that ice could reform further south as snow, cooling the planet significantly.


Of course, a sufficiently large volcanic eruption could cause an ice age by itself. But with so much water freed from the poles by global warming, much smaller eruptions—which happen every few years—could have the same effect, raising the likelihood of an ice age.