Climate change and winter


in Canada, Politics, Rants, Science, The environment

Cracked wood

During the last few days, I have had a depressing number of people approach me quasi-triumphantly, pointing to either the CRU emails or the first winter snowfall as evidence that climate change is nothing to worry about.

Both comments are worrisome, given that we are in the midst of negotiations at Copenhagen that will play a significant role in determining whether we keep temperature rise under 2°C or not. The CRU emails already have a post of their own, but I thought I would say a couple of things about winter.

The latter argument – about the snow – is especially absurd. Climate change is about a shifting distribution of temperatures. There will always be extremes of hot and cold, it’s just that the former are becoming more frequent relative to the latter. That said, I recall reading about a study that found that most Canadians cannot explain why there are seasons at all, with a plurality offering the theory that is has to do with the distance between the Earth and the sun. Of course, our winter is summer in the southern hemisphere, which shows that this hypothesis cannot be valid. Winters are the consequence of the fact that the Earth rotates on an axis that is presently tilted 23.44° off from the direction of our orbit. That makes the length of days variable, and changes how the distribution of temperatures across the globe plays out. That level of tilt varies across geological time due to tidal forces. When the tilt is greater, the variation between the seasons is alo larger; when the tilt is lesser, the weather towards the poles remains more consistent year-round. The level of tilt has an affect on processes like glaciation.

This will continue to happen essentially forever, regardless of how much warming we experience. The distant polar regions will always experience months of darkness, and will thus always be colder than the equator during those spans. Indeed, this is a nice demonstration of what a massive amount of energy the sun adds to the Earth system. None of this disproves the fact that greenhouse gasses being added to the atmosphere warm the planetary system overall.

The two queries also highlight some potentially important psychological issues. People on both sides of the argument are sometimes overly quick to grab at any piece of evidence that seems to support what they already believe. In his book, Greg Craven goes on at some length about the importance of this ‘confirmation bias.’ Such sloppy reasoning is one reason why the climate change debate is so flawed. Hard as it can be to do so, we need to question data and sources of information even when they seem to confirm our existing beliefs – just as we must take into consideration sources and data that seem to contradict what we hold to be true. That doesn’t mean, however, that we should remain paralyzed forever, unable to take action due to uncertainty. We take precautionary action on the basis of uncertain threats all the time. A risk management approach to climate change is one where the preponderance of evidence is sufficient to drive preventative action.

Above and beyond that, I think the fact that people cheerily point to a snowfall to argue that the planet isn’t in danger shows that they don’t yet seriously appreciate how dangerous climate change could be. The fact that it is still often treated as a half-joking matter bodes ill for our ability to put our society on a course where the largest risks of catastrophic or runaway climate change can be avoided.

{ 12 comments… read them below or add one }

Milan December 9, 2009 at 10:47 am

There will always be extremes of hot and cold, it’s just that the former are becoming more frequent relative to the latter.

Andrew Weaver’s book has a good discussion of this, near the beginning.

This chart I made illustrates the point about a shifting distribution.

. December 9, 2009 at 12:00 pm

Climate change: Scientists say this decade likely hottest on record

At Copenhagen climate change talks, a research group says this decade is likely to prove the hottest on record.

COPENHAGEN, DENMARK — The first decade of the 21st century is shaping up to be the warmest decade on record globally, while 2009 is likely to crack the Top 10 list of warmest years, perhaps rising as high as No. 5.

That’s based on a preliminary look at global climate trends released today by the World Meteorological Organization (WMO) at global climate change talks here in the Danish capital. The WMO’s data stretches back to 1850.

The numbers are subject to revision, cautions Michel Jarraud, the WMO’s secretary-general. A final analysis of the year and decade is due out next March. Still, he says, the figures released today “are pretty solid.”

Tristan December 9, 2009 at 3:51 pm

“or the first winter snowfall”



Although, in some sense, it’s easy to see where this reasoning originates. Tell me if you think this is anything like what’s happening –

p1. Scientists claim 2009 is on track to be the warmest year on record, or one of the warmest (it was one of these) (true, I think)

p2. Toronto has its first snow-free november since 1847 (true, I heard on the radio)

c1. Toronto has its first snow-free november since 1847 because 2009 is one of the warmest years on record (fallaciously inferred from 1 and 2)

c2. The temperature in my city is directly related to global climate (fallaciously inferred from c1)

p3. Global warming means it gets warmer every year. (blatantly false)

p4. Interpretation: “gets warmer every year” means every day, month, season this year is warmer than last year (blatantly absurd interpretation)

p5. Today it is colder than the same day last year in Ottawa. (certainly true on numerous days every year regardless of overall city or global trend)

C3. Global warming is false or has stopped (from P3, P4, P5 and C2)

Milan December 9, 2009 at 4:05 pm

I don’t think people are reasoning in logical chains. I think they are unthinkingly grabbing for any data that seems to support a position that they would like to be true.

It happens all the time, and is a significant basic failing of most human reasoning.

R.K. December 9, 2009 at 5:12 pm

It’s pathetic that this argument still circulates. It certainly demonstrates that people are generally pretty poor interpreters of data, at least when they are thinking about it in a way that is not systematic.

R.K. December 9, 2009 at 5:13 pm

Nice photo incidentally.

Very harrowing.

Milan December 9, 2009 at 5:33 pm

People need to be more responsible about how they think about climate change.

For those trying to do so, Greg Craven’s book and videos are a good resource.

This issue is too important to have a semi-formed opinion about, backed with whatever evidence you have happened across at random.

Tristan December 10, 2009 at 2:45 pm

“I don’t think people are reasoning in logical chains.”

I think you’re right, I was foolhardy to try to still the reasoning. However, I still think this chain captures many of the fallacies employed.

Milan December 10, 2009 at 2:48 pm

Confirmation bias is a really enormous problem, when it comes to all sorts of complex issues. It is extremely easy to spend your life noting every news story and bit of data that confirms your view, while simply ignoring or downplaying those that do not.

One of the most valuable things about maintaining a blog is that I get critical comments that force me to defend my positions and think about contrary evidence.

. January 12, 2010 at 8:00 am


Jan 11th 2010
Britain’s cold snap is explained by the Arctic oscillation

IT IS an ill wind that blows no good, as people have been remarking to each other since at least the 16th century. In the case of the bitter easterlies that have brought Britain colder, snowier weather than has been seen for a couple of decades, the proverbial benefit has been felt by the more foolish and facile of those who doubt the reality or likelihood of man-made climate change. “Snow Chaos: And still they claim it’s global warming” read the front page headline of Britain’s Daily Express on January 6th. The foolishness is not one sided. With less public prominence, those convinced of climatic doom mutter of “extreme events” being more likely in a more man-made climate, with the implication that this might in some way explain the current cold.

To try to make a climatic point either way out of a patch of unusual weather, though, is normally to be on a hiding to nothing, and so it is this winter. No one with any claim on the public’s respect has ever said that all of the natural ups and downs of climate will be ironed out onto a smooth upwards trend by greenhouse gases; their effects are expected to show up not so much in particular events, but in statistics. The reverse of the same coin is that there will still be cold snaps in a warming world. But that is not to say that the current cold might not have implications beyond the spring, or that it might not help explain more about how the climate actually works.

The two effects brought on by the extreme negative mode of the AO thus could cancel each other out. But it is also possible that one or other of them will win through, with a significant effect on this year’s summer ice. To some people, including, almost certainly, those who write the headlines in the Daily Express, the fact that the same phenomenon might explain either record low sea ice or continued recovery of sea ice will be seen as inconsistency, poor science, or something more suspect. To people actually interested in how the climate works, however, seeing what happens in a very strong negative AO may prove a boon, by allowing the roles of different processes in ice loss to be further disentangled. Weather and climate are not the same, but there are links between them in both directions—links which can usefully be understood.

. January 12, 2010 at 1:37 pm

Of climate, weather and Arctic blasts

Well, if you live in the Northern Hemisphere, you’ll have noticed it’s colder than usual. Some countries have been turned white for several weeks with snow falling, but not melting at all. In the Netherlands, where I live, the entire country seemingly stopped moving for a few days before Christmas, both enchanted by the winter wonderland, and having roads and train tracks completely blocked by the snow.

This has been going on for about a month, which is an unusually long time for us to bear the inconvenience and disruption which results, but an extremely short period on the time scale with which climate is analysed – one point on the charts, which, against a perpetual background of natural variation, are nonetheless showing an ongoing upward trend over time-scales of years to decades. The current cold snap is part of that natural short-term fluctuation which we will always face, even in a future world which, on the basis of global, long-term averages, may be much warmer than present. And while it might seem that the entire globe is caught in its icy grip, it is actually a far more regional phenomenon than might immediately be apparent.

The extreme cold weather has been caused by an extremely interesting (yet not so well understood) weather pattern called the Arctic Oscillation. Simply put, a pattern of high atmospheric pressure over Greenland and parts of the Arctic has been blocking the usual pattern of much milder south westerly winds from the Atlantic and instead sending cold northerly and easterly winds to lower latitudes from the Arctic and the northern European land masses. At the same time, however, this same high pressure system has been causing much higher temperatures than usual in parts of the Arctic, but since population density is obviously much lower there, we haven’t heard as much about these. Furthermore, during the last week of December when the cold weather across Europe began to take hold, many parts of the North East USA and Canada, as well as North Africa, the Mediterranean and large areas of South West Asia were a good few degrees warmer than usual, up to 10 degrees Celsius warmer in parts of Northern Canada.

Despite the Arctic Oscillation being a known (if unpredictable) weather pattern, this hasn’t stopped would-be witty headlines all over the world, wondering what happened to global warming, worrying we are now entering global cooling etc. – all more designed to attract readership and page views than to reflect scientific knowledge. The old adage – never let the truth get in the way of a good story – is hard at work.

. March 10, 2010 at 4:51 pm

Environment Canada scientists report that winter 2009/10 was 4 C above normal, making it the warmest since nationwide records were first kept in 1948. It was also the driest winter on the 63-year record, with precipitation 22 per cent below normal nationally, and down 60 per cent in parts of Alberta, Saskatchewan and Ontario.

“It’s beyond shocking,” David Phillips, a senior climatologist with Environment Canada, told Canwest News Tuesday. Records have been shattered from “coast to coast to coast.”

“It is truly a remarkable situation,” says Phillips, noting that he’s seen nothing like it in his 40 years of weather watching. He also warns that “the winter than wasn’t” may have set the stage for potentially “horrific” water shortages, insect infestations and wildfires this summer.”

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