Modelling the climate

Tom James @ 02-07-2009

weatherAn interview with Gavin Schmidt over on Edge explores the nature and development of climate modelling:

What we have decided, as a scientific endeavor, is to extrapolate as much as we can from our knowledge of the individual processes that we can measure: evaporation from the ocean, the formation of a cloud, rainfall coming from a cloud, changes in the wind patterns as a function of the pressure field, changes in the jet stream. What we have tried to do is encapsulate those small-scale processes, put them altogether, and see if we can predict the emerging properties of that fundamental complex system.

He explores the sometimes contradictory predictions of different climate models:

In the same way that you can’t make an average arithmetic be more correct than the correct arithmetic, it’s not obvious that the average climate model should be better than all of the other climate models. So for example if I wanted to know what 2+2 was and I just picked a set of random numbers, the answer by averaging all those random numbers is unlikely to be four. Yet when you come to climate models, that is kind of what you get. You get all the climate models and they give you some numbers between three and five and they give you something that is very close to four. Obviously, it’s not pure mathematics — it’s physics, it’s approximations, there is empirical tuning that goes on.

You need to have some kind of evaluation. I don’t like to use the word validation because it implies a kind of binary/true-false set up. But you need an evaluation; you need tests of the model’s sensitivity compared to something in the real world that can give you some credibility that that model has the right sensitivity. That is very difficult.

It is a lengthy essay/video interview but well worth the read/watch, as it is refreshing to hear firsthand from a professional climatologist.

[at Edge][image from Nicholas T on flickr]


Is geoengineering our last worst hope?

Paul Raven @ 27-02-2009

Whatever you think might have caused global climate change, you’d be hard pressed to claim that we don’t need to do something about it – after all, we don’t yet have another planet to go to, and the results are going to have real effects on real people.

But what are our options? Emissions controls would be a great start, but we’re struggling to get any political agreement on how much and how soon, and the clock is ticking all the while. Hence the increasing prevalence of suggestions from the field of geoengineering – planet-hacking, in other words.

New Scientist has a lengthy article looking at the potential pitfalls of geoengineering, which include not just the risk of tweaking something the wrong way and making things worse (whether for everyone or just a certain locality) but the inevitable geopolitical hazards. Not every nation has the resources to take direct action at the required scale, and – because that action could affect the rest of the planet in unexpected ways – no one’s going to be happy with any nation (or group or individual) that decides to jump the gun and take matters into its own hands.

It’ll be a while before these questions work their way into mainstream politics (especially considering the rather more immediate  issues of the financial implosion), but I doubt it’ll be all that long in real terms – nor does Jamais Cascio, who has been beating the drum about geoengineering for a good few years already. That the scientific field is starting to consider geongineering as a serious option is a sobering thought – these are the guys who know the system best, and if they’re suggesting jury-rigging might be our only way out then things may be grimmer than anyone is willing to admit.

[Yes, this post is predicated on the notion that climate change is a genuine phenomenon, a genuine threat and likely human in origin. As much as I respect your right to disagree with any or all of those three statements, if that’s all you have to bring to this discussion I’d like to ask you to sit it out for once. Cheers.]


Don’t burn all the fossil fuels (yet)

Tom James @ 19-02-2009

icebergAccording to Professor Gary Shaffer of the University of Copenhagen we should stop burning fossil fuels now so that we will have enough coal, oil, and gas left when we need to fend off the next ice age over the next several hundred thousand years:

…for a management scenario whereby fossil fuel use was reduced globally by 20% in 2020 and 60% in 2050 (compared to 1990 levels), maximum global warming was less than one degree Celsius above present. Similar reductions in fossil fuel use have been proposed by various countries like Germany and Great Britain.

In this scenario, combustion pulses of large remaining fossil fuel reserves were then tailored to raise atmospheric CO2 content high and long enough to parry forcing of ice age onsets by summer radiation minima as long as possible. In this way our present equable interglacial climate was extended for about 500,000 years, three times as long as in the “business as usual” case.

Nice to see some people are cranking up their Buxton indices into the 100, 000 years range.

[via FuturePundit][image from nick  russill on flickr]


Exhaust fumes are lightning magnets

Paul Raven @ 19-01-2009

rural lightning strikeChalk another item up on the list of environmental effects caused by car exhaust fumes – they increase the likelihood of lightning strikes.

“In the south-eastern states [of the US], lightning strikes increased with pollution by as much as 25 per cent during the working week. The moist, muggy air in this region creates low-lying clouds with plenty of space to rise and generate the charge needed for an afternoon thunderstorm.

Surprisingly, the effect was not strongest within big cities with high pollution, but in the suburbs and rural areas surrounding them… “

Now there’s a tenuous techno-thriller plot device just waiting to be used… I wonder if a big enough car-generated lightning storm could deflect an incoming NEO? Call Bruce Willis! [story via BLDGBLOG; image by M0i et c’est tout]


Global warming argy bargy

Tom James @ 12-11-2008

A study suggests that long-term changes in the Earth’s orbit would have resulted in an ice age between 10,000 and 100,000 from now, if it were not for the effect of anthropogenic global warming:

The chill would induce a long, stable period of glaciation in the mid-latitudes, smothering Europe, Asia and North America to about 45-50 degrees latitude with a thick sheet of ice.

However, there is now so much CO2 in the air, as a result of fossil-fuel burning and deforestation, that this adds a heat-trapping greenhouse effect that will offset the cooling impacts of orbital shift, said Crowley.

“Even the level that we have there now is more than sufficient to reach that critical state seen in the model,” he said. “If we cut back [on CO2] some, that would probably still be enough.

Apparently this isn’t an excuse to continue venting CO2:

Crowley cautioned those who would seize on the new study to say “‘carbon dioxide is now good, it prevents us from walking the plank into this deep glaciation’.”

“We don’t want to give people that impression,” he said. “(…) You can’t use this argument to justify [man-made] global warming.”

[story at Physorg][image from Pear Biter on flickr]


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