The polar vortex in no way disproves climate change
Almost half of the Lower 48 will shiver under sub-zero wind chills Tuesday morning. Countless records will be set. Yet none of that means a thing about the existence of climate change, its severity or its consequences.
GFS model shows polar vortex over northern U.S. and southern Canada this evening (WeatherBell.com)
The breaking off of a large chunk of the polar vortex and its visit to the northern U.S. is a random event resulting from a serendipitous arrangement of weather systems. In short, the clockwise flow around giant areas of high pressure over Alaska and west of Greenland have forced the atmosphere’s steering currents to shove the vortex into the northern U.S.
It happened before humans dumped billions of tons of carbon dioxide into the atmosphere and will happen again.
This polar vortex excursion is a single weather event directly affecting about 2 percent of the world.
Climate change is measured by evaluating continental to global trends in weather over decades – not events happening over a few days in a little region. For this reason, a fleeting cold wave (or snowstorm) over part of a continent should never be used as evidence for or against climate change.
The record shows winter temperatures have risen markedly in recent decades across the northern hemisphere.
Northern Hemisphere temperature difference from 20th century average 1880-2013. (NOAA)
Winter warming over the U.S. (Climate Central)
In short, climate change has reduced the intensity/frequency of cold extremes averaged over time. But that doesn’t mean they’re over or have been eliminated. Events like the record cold in Europe in 2011 and this polar vortex event are clear examples of the exceptional cold weather extreme in a warming world.
(Were it not for the build-up of manmade greenhouse gases in the atmosphere, I’d posit the extreme cold events we witness now would be even colder. In other words, take these same cold air outbreaks and project them on the climate of the 1800s, and they’d be more severe. We’d need a model to test that, but it’s an educated guess.)
The truth is that increasing greenhouse gases act to warm the globe and, on average over time, should take an edge off the cold. But the planet is a really big, complicated place and the weather changes fast and randomly. Conversely, the climate changes very gradually. Taking all of this together, cold shouldn’t come as a shock, nor should it have anyone second-guessing the reality of climate warming.
Fonte: washingtonpost.com
