Saturday, April 21, 2012

Jigsaw puzzle



You open your new 1,000 piece jigsaw puzzle and tip the pieces onto the table making a messy pile of colours and shapes. One by one, you fit them together and the picture begins to emerge. Way before the end, you can see the big picture, but it is not until the last piece goes in that all the details are evident.

Scientists describe climate change as a jigsaw puzzle with thousands of pieces.

Climate scientist Michael Mann says:
... the evidence for human-caused climate change is more like a vast puzzle, a few pieces of which come from paleoclimate data like what my colleagues and I studied in our hockey-stick paper.

Meteorologist Paul Douglas says:
The changes we’re seeing, far more than I can list here, seem like an accumulation of coincidences. Pieced together, reveal the full puzzle: There’s more heat and moisture in the atmosphere, and our emissions are largely responsible for keeping it there.
 Paul Douglas in Bloomberg News

Climate Bites  contrasts the jig saw approach with the house of cards approach to science. House-of-cardists busily attack a single element believing it will bring the whole house down. Jig-sawists point out that climate science is not like that. 

In testimony before Congress in 2010, Nobel-lauriate Mario Molina described his jigsaw analogy this way (via Dot Earth, Andy Revkin). 
There appears to be a gross misunderstanding of the nature of climate change science among those that have attempted to discredit it. They convey the idea that the science in question behaves like a house of cards: if you remove just one of them, the whole structure falls apart.

However, this is certainly not the way the science of complex systems has evolved. A much better analogy is a jigsaw puzzle: many pieces are missing, and some might even be in the wrong place, but there is little doubt that the overall image is clear, namely that climate change is a serious threat that needs to be urgently addressed.

It is also clear that modest amounts of warming will have both positive and negative impacts, but above about 4 or 5 degrees Fahrenheit most impacts turn negative for many ecological systems, and for most nations.


Climate change deniers like to pretend that the climate science rests on one or two pieces of evidence and they keep attacking the same one or two things. They're looking at a kindergarten puzzle with only two or three pieces, but the vast complexity of atmospheric physics and planetary climate systems are more like those 1,000 piece jigsaw puzzles with no straight edges.

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