Thursday, March 11, 2010

Cherry Picking Data

As the phrase goes; there are lies, damn lies and statistics. If you don't know much about statistics then it can be used to confuse and obfuscate. A classic of denialist obfuscation is the meme that there has been no warming since 1998. When you plot the temperature changes over time it looks like nothing much is changing:

The argument then goes; well as there's been no warming since 1998, climate change must have stopped. This clicks my bullshit detector into the red; why pick 1998? Why not 1990 or 1995? In fact why not 1880? 1880 is a good year to start from because that is the year we started collecting accurate records of global temperatures.

So how does the post 1998 temperature meme look in the full context? Lets see how post 1998 stats look on this scale.. since 1880:

Plot the all of the data into a graph since 1880 and it all looks very different:

And here is the same graph with the trend line added:

The idea of using post 1998 temperature now looks pretty feeble. It is also clear that the reason 1998 is picked by denalists is that that is the point from which they can build be best pseudo-case of 'warming has stopped'. Problem is, it has not and is on-going.

There are liars, damn liars, and climate change deniers.

The reality is much more scary.


Ellipses said...

That was succinct. Good show!

Anonymous said...

Thank you.

Anonymous said...

"1880 is a good year to start from because that is the year we started collecting accurate records of global temperatures"

Are you kidding? Tell me you're joking. You don't actually believe this surely? Claims like this are why the skeptics are winning the climate change battle. In 1880 thermometers were not accurate at all. They were just a tube of mercury with a bunch of scratches on the side, and there were only a few places in the world which recorded temperatures on a regular basis; mostly eastern European, N American and some Asian universities representing about 5% of the earth’s surface. You can’t possibly stretch this enough to call it global in scope. There were no global temperatures measured until satellites were used in the 1970’s. That’s about 40 years.

Anonymous said...

Anonymous (3),

The global average temperature was known with less accuracy in 1880 than in 2000. True enough, and known (see eg the green error bands on this figure:

But you seem to confuse uncertainty with knowing nothing. A common mistake.

Bart Verheggen

anarchist said...

Thanks Bart! Good answer.

I see this a lot in the debate the idea that if an individual does not understand a concept then it can't be true.

Anonymous said...

606, I think it's absolutely wonderful that you are still banging on about this, you're not obsessed or anything.

Your old friend Joe Bloggs

Ps Do you know any Mexican experts on Glaciers I could consult to cure my evil sceptic ways ;-)

anarchist said...

Hi Joe,

Here's an interesting glacier story from Bolivia to keep you going:

Anonymous said...

That must have kept you busy finding that, which of course in no way changes the fact that the IPCC has had to revise it's views on glacier retreat,anyways,here's one from todays news for you to think about