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Hello fellow scientists! Thanks to your active collaboration, our study-- the world's largest
uncontrolled experiment-- crossed a historic milestone on May 9, 2013. Ahead of schedule,
the concentration of carbon dioxide gas in the Earth's atmosphere has reached 400 parts
per million.
This is a big change from a hundred years ago when the concentration was just 300 ppm,
below which it had stayed for more than 800,000 years. We've used the most effective methods
to increase the levels of CO2 in our atmosphere: burning coal, oil and natural gas, chopping
down forests, and surprisingly, making cement.
In some respects 400 ppm is just an arbitrary figure, an attractively round number like
the four-minute mile or the 7 billion mark for world population, but it indicates that
we have reached a new phase of our experiment. Each day forward, we go deeper into territory
uncharted in human history! After 400 ppm, who knows what will happen!?
Actually, our preliminary results give us a pretty good idea. We've seen more and bigger
floods, fires, droughts, and storms. Melting ice caps and rising sea levels. You may already
have experienced some of these yourself, and you can expect more in the future.
Please publicize our experiment and tell your friends, family, and politicians how important
their contributions have been. After all, it is people -like you and me and major corporations-
with access to cars, air conditioning, and supermarkets, who are responsible for the
large majority of today's greenhouse gas emissions.
This global experiment can't continue without your participation. So remember, the next
time you let your car idle, leave the AC on when you're not home, or forget to eat the
food you bought... you're part of something big.