Tuesday, November 22, 2016

Global sea ice has reached a record low – should we be worried?

I suggest reading the whole article. It's not long, but is informative.


Nov. 21, 2016
New Scientist
By Michael Le Page


This is a weather event, not a climate event

What’s happening in the Arctic would be impossible without a century of global warming causing a long-term decline in sea ice levels — but it is actually a short-term weather event.

At this time of year, sea ice should be growing rapidly as winter sets in. But the cold air that usually sits over the pole has flowed south over Siberia, while warmer air has flowed north. This has resulted in temperatures an astonishing 20 °C warmer than usual, so sea ice is melting when it should be forming.


In fact, it’s two weather events

On the other side of the planet, the sea ice around Antarctica is falling during the southern summer. The sea ice reached its maximum winter extent unusually early this year and has been falling fast, to a new record low for this time of year (see graph below).


So, sea ice levels at both poles are much lower than the seasonal average.

Antarctic sea ice levels have actually been increasing slightly over the past three decades, so this low is unusual. The increase could be due to a combination of stronger winds spreading out the sea ice and fresh water from melting ice on land diluting seawater so it freezes at higher temperatures.


Global warming may be making freak weather events in the Arctic more likely

All weather events are influenced by climate change as they now take place in a world more than 1 °C warmer than a century ago.

There is growing evidence that the crazy weather we’re seeing in the Arctic and surrounding regions is made far more likely by climate change. Normally, cold air is kept locked up in the Arctic by a spinning vortex of air bounded by fast winds high in the atmosphere called the jet stream.

Now, more and more often, the jet stream seems to weaken and allow cold Arctic air to flow south, with warm air flowing north to replace it. This odd jet stream behaviour could be to blame for many of the freakishly cold weather events in recent years as well as current events.
Yes, we should be worried

What’s happening now is alarming, but it’s not the short-term craziness we should be worrying about. The reason to be alarmed is that this kind of event can happen only because the planet is so much warmer than in pre-industrial times.


The loss of sea ice does not directly raise global sea levels, but it is already affecting us all through its effects on the weather. As the planet continues to warm we are going to see even more freakish weather.

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