2010-10-23 03:11:17Isn't a few C of warming really small?
MarkR
Mark Richardson
m.t.richardson2@gmail...
192.171.166.144

Isn’t global warming just 2 oC, and isn’t that really small?

21 oC isn’t much different from 19 oC: either way I’ll wear a t-shirt. Plenty of “sceptical” articles mock such small changes in temperature: after all, we expect more warming in cooler places and at night, which surely isn’t a problem.

There are three main problems with even small sounding global warming. Firstly, 2 oC is a very optimistic assessment of global warming. If the sceptical Dr Roy Spencer is correct, we’re currently on course to get more like 3.5 oC. If mainstream climate science is correct, we’re on course to 6 oC by doubling CO2 twice.

Secondly, if we cause a ~2 oC warming, this is the region where scientists fear serious feedbacks have a chance of kicking in; such as melting permafrost releasing methane, a potent greenhouse gas. Ice and sediment cores suggest we haven’t been this warm in at least 600,000 years, so we’re not too  sure – but this could trigger a lot more warming.

Finally, 6 oC, the actual “best estimate” for eventual global warming from current CO2 trends might still sound small. But heating isn’t distributed evenly: in the past, a 6 oC global change was what got us out of the last ice age. 6 oC global change sounds small, but for people living in Northern Europe and Canada it’s the difference between walking around in a t-shirt and a mile of ice over your head.

The graph below is the temperature calculated over the past 400,000 years in Antarctica from the Vostok ice core. The tiny peaks are a bit like today and the tiny troughs would likely make the homes of hundreds of millions of people uninhabitable. So yes, a few degrees C of global warming can mean a lot.

 

(Insert graph of Vostok data rescaled and links to papers/articles)

 

 

 

I whipped this up after reading some more idiocy from Eschenbach here. Sure, he sounds reasonable to people who are a bit ignorant, but I think the comparison to recent glacials is a good image to help people understand what will actually happen.

2010-10-23 03:33:38
nealjking

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in http://www.skepticalscience.com/thread.php?t=91&r=9, I argued that a 1-C temperature increase corresponds to an isotherm shift poleward of roughly 150 km; or to a climb of about 100 m in altitude. This is a big move for a forest, even if it has to be done at a rate of 0.1-C/decade.

I expect to write this up when a few urgent tasks are over.

2010-10-23 06:36:51
Rob Painting
Rob
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118.93.215.69

6 oC global change sounds small, but for people living in Northern Europe and Canada it’s the difference between walking around in a t-shirt and a mile of ice over your head.

That's a great line. And weren't sea levels during the Pliocene 25 meters higher than today, when it was globally 2 -3 degrees warmer?.

2010-10-23 10:25:02Comment
Robert Way

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134.153.163.105

 Another thing you should note is that people quibble about whether 2 degrees will doom the ice sheets but 6 degrees certainly will.

2010-10-23 16:17:57Very glad to see a post on this. The WUWT post makes me angry
John Cook

john@skepticalscience...
124.186.160.198
Here is another take on this argument. I know you're getting lots of different suggestions so follow your own judgement on how best to approach it. My thoughts are a little disorganized too so take them as a 'rough draft' kind of argument:

Comparing weather temperature changes to global temperature change is like comparing apples to oranges. Weather changes are due to heat 'sloshing' around from place to place and while a single location can change temperature dramatically, the overall amount of heat in our climate system hasn't changed. Global temperature on the other hand is due to the planet accumulating heat. Since 1950, the planet has warmed only 0.6 degrees [check this figure, I'm guesstimating]. However, most of this warming, over 80%, has gone into the oceans. The amount of heat pouring into the oceans is around 140billionwatts [again, guestimate]. This is equivalent to 140,000 nuclear power plants all simultaneously pouring their output into the oceans.

why does this matter? There are many impacts from this build up of heat but just one of concern is the effect of the warming oceans on ice sheets. The warmer water is causing ice sheets to slide faster into the oceans. This means the Greenland and Antarctica ice sheets are losing ice mass at an accelerating rate. How much ice mass do we expect these ice sheets to lose? 120,000 years ago [guestimate], global temperatures were 2 degrees warmer than preindustrial levels, or just 1.2 degrees warmer than now. 1.2 degrees warming doesn't sound like much - we experience more warming every morning. But globally, it meant such a build up of heat that the ice sheets melted substantially. How much? Sea levels were 6 to 9 metrses higher than current levels.

so if anyone who tells you 1 or 2 degrees warming doesn't matter, point them to the past. Show them how 2 degrees warming means at least 6 metres sea level rise. To compare global warming to weather temperature changes is misleading and turns a blind eye to what past climate change tells us.

2010-10-23 17:37:07
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.215.69
A graphic to illustrate Mark's line, or the difference between sea levels would sure have some impact. And of course it's something I wouldn't have a clue how to do (yet).
2010-10-23 19:44:49
MarkR
Mark Richardson
m.t.richardson2@gmail...
134.225.187.80
I found some cool diagrams and saved them. I'll put this post up on Monday and I like John's description so I'll try to add that in too!
2010-10-23 21:38:30
nealjking

nealjking@gmail...
84.151.50.86

Well, John, the fact that WUWT is resorting to arguments like this is just predictable, and suggests to me that they're trying to deal with the inescapability that GW is actually happening.

For a long time, the line of retreat has been projected as follows:

- GW is not happening

- GW is happening, but it's not due to us

- GW is due to us, but it won't be that bad, might even be good

- It's too expensive to do anything about GW

- It's too late to do anything about GW

- Sh*t, we need to do something about GW

We are at about stage 3; we will not get to stage 6 until we've passed through the intervening stages.

 

2010-10-28 10:20:47Have published this is a rebuttal
John Cook

john@skepticalscience...
124.186.160.198
http://www.skepticalscience.com/few-degrees-global-warming.htm