What We Don't Know

How did life begin? What's the universe made of? Why do we sleep? 42* of the biggest questions in science.

Why can’t we predict the weather? 

Wired, Issue 15.02 - February 2007

http://archive.wired.com/wired/archive/15.02/bigquestions.html?pg=3&topic=bigquestions&topic_set=

A few years ago, weather forecasts 

were totally unreliable beyond a couple of days; 

today better computer models 

make them accurate as far as a week out. 

That’s fine for figuring out 

how to pack for a business trip 

or whether you need to rent 

a big tent for the wedding reception. 

The trouble starts 

when you want to build 

a computer model to predict 

the weather over decades or centuries. 

In 1961, a meteorologist 

named Edward Lorenz 

was running a computerized 

weather simulation and decided 

to round a few decimal places off 

one of the parameters. 

The tiny tweak completely changed weather patterns. 

This became known as the butterfly effect: 

A butterfly flapping its wings in Brazil 

sets off a tornado in Texas. 

Lorenz’s shortcut 

helped launch chaos theory 

and sparked an obsession 

among meteorologists 

with feeding as-perfect-as-possible data 

into their models in an attempt 

to lengthen their forecast window.

But even refining precision 

doesn’t get us to long-term prediction. 

For that, climatologists 

need to understand boundary conditions, 

like the interactions between 

the atmosphere and the oceans. 

The goal, says Louis Uccellini, 

director of the National Centers 

for Environmental Prediction, 

is to model Earth 

as a single climate system. 

Then we can figure out what’ll happen to it next.

- Lucas Graves