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.