2010-09-15 11:33:18Common skeptic question - do a few degrees of warming matter?
John Cook

A commenter asks the question why does the small temperature change matter? It's a good question - if temperature changes up to 20 to 30 degrees over a 24 hour period at a single location, why is global warming of 1 to 2 degrees such a big deal? It's just 1 degree!!

KR answers with regard to glacial growth, that it's the change in accumulation/reduction rate that matters. But more generally speaking, I've thought in the past that it would be good to write a rebuttal to the argument "A few degrees of warming doesn't matter". Can I post my initial thoughts on how I would approach this rebuttal, open it up for other thoughts then one of us can bring it all together in a single rebuttal?

I'd point out that day to day weather variations are the result of internal variation - heat "sloshing around" as James Hansen puts it. But global warming is a result of the planet overall building up heat. Most of this heat goes into the oceans so a few degrees of warming of air temperature equates to huge amounts of heat building up in the oceans. Just one effect of all this extra ocean heat is that warming ocean water causes glaciers to slide faster into the ocean - thus we're seeing accelerating ice loss in Greenland and Antarctica. So what effect does a couple of degrees of global warming have? Back in the last interglacial, just over 100,000 years ago, global temperatures were around 1 to 2 degrees warmer than now. At that time, sea levels were at least 6 metres higher than now, due to ice loss from Greenland and Antarctica. That is the very real, tangible effect that a few degrees of global warming will have.

An idea - I could always invite Mark Lynas, author of 6 degrees, to write the advanced version of this rebuttal. Maybe unrealistic but worth thinking about. Thoughts, comments, other takes on the subject matter?

2010-09-15 15:20:12Lynas!
Dana Nuccitelli

Lynas' book was great - it would be cool to get him as a guest author.

My response to this is that the planet only warms about 6°C on average from glacial to interglacial (assuming this guy John Cook knows what he's talking about!), so clearly a couple of degrees is a big deal on a global scale.

2010-09-15 15:39:39Ice age warming
John Cook


Good point - the difference of 6C is the difference between a global ice age and a balmy interglacial. That's a good point to mention in this rebuttal.

My 6C figure is something I heard from a guy who heard it from a guy. Well, not that indirect, I just can't recall who told me or where they got the reference from. Sounds about right though - if Antarctica warmed 10C and taking into account polar amplification.

2010-09-15 17:55:38


- delta of -6 deg-C during Ice Ages: I was just looking into that; I think the wiki for the topic gives a reasonable start. Keep in mind that an average can hide information as well: Some warm areas may have hardly been affected, and that would keep the average temperature higher.

- Lynas: I have his book somewhere, but it's hiding. In the meantime, there's a summary here: 


But getting him to do an Advanced version would be super. (Although I don't know if it really has to be Advanced: I don't see how it could be that hard to understand the implications. Maybe it's more "Detailed" than "Advanced" in this case? Words!)

- My pet peeve: Ecozone displacement. 0.1-deg-C corresponds to about a 15 km shift poleward, or 10 meters upward. See the thread proposing a new series, and here. But I am hoping to hear from Moth Incarnate: no word for some time. So a 1-deg-C shift would be 150 km polewards, or 100 meters upward. How will trees do that?

2010-09-15 19:47:28How trees migrate
John Cook

Haven't you seen Lord of the Rings? :-)
2010-09-15 20:34:38


Yeah, good luck with that.


2010-09-16 02:38:57

Well,  on a practical scale of plain old weather, Russia this summer is a good example of why a few mean degrees or even 10ths of a degree matter. Pakistan, Qatar, the list is quite extensive. We're not talking about a nice, smooth rise in temperatures across the globe,  synchronous and with perfectly even distribution. Extra energy gets concentrated in locations and ways that cause damage to exceed the envelope to which we're accustomed. On a time scale of a single lifespan, extremes matter and those are how most of us are going to experience the unfolding of changing climate.
2010-09-16 13:34:02
Rob Painting

As Doug points out, a 1 degree increase in mean global temperature won't be distributed evenly over the Earth. The poles and continental landmasses will see a bit more than that.

I had a fiddle with that Climate Wizard tool, but couldn't figure out how to induce a mean 1 degree increase in global temp, to see what the future may hold, however the UK Met Office/Hadley animation, suggests a further 1 degree increase (from 2008) would add another 8 -12 degrees C to the high Arctic circle, and 2 degrees over much of the continental land masses i.e. where we might be in about 25 years time.

Some further context for your post might be useful too, consider the marked changes in the we've observed in the last hundred years with less than a degree of warming.

What will a further degree warming do to the coral reefs?. Further intensification of the hydrological cycle - more intense droughts & precipitation events & a decline in crop yields and productivity? , continued expansion of the storm tracks towards the poles, greater storm intensity due to the greater energy available. . Basically every negative impact of warming we are currently experiencing will be amplified.

There's also the probability we step closer, or over tipping points such as initiating the eventual loss of the Greenland Ice Sheet, and unlike the last interglacial, it won't be saved by changes in the Earth's orbit.

Be interesting to see what you come up with, but by time we see another degree of warming the surviving skeptics will have scattered like cockroaches when the light is turned on.

2010-09-16 21:57:05doug_bostrom


made the interesting point that:

"We're not talking about a nice, smooth rise in temperatures across the globe,  synchronous and with perfectly even distribution. Extra energy gets concentrated in locations and ways that cause damage to exceed the envelope to which we're accustomed."

Now this point is not really surprising (I even hinted at the similar point about how the averages hide information, meaning the extremes), but what would really bring the point home would be some explanation and examples of what the extremes could look like, during the same time, and WHY. If someone knows some hardcore climatology and can go into meaty detail about HOW "extra energy gets concentrated in locations and ways", as doug mentioned above, it would be super: someone who can give some idea about the mechanics/dynamics involved.

These examples would give some punch to the point that even though the average temperature was only 6-deg-C lower during the heart of the last ice age, in large regions it was frigging cold.

 Is there a climatologist in the house? Preferably one that also knows something about weather.