Here’s a template for a letter I hope you will consider sending/emailing to all of your elected representatives at the municipal, state, and federal levels, if you are in the US. Thanks

Dear [elected official]

I am writing to ask you to join the very small but hopefully growing number of elected representatives and executives in noting the important news this week regarding the human contribution to the amount of atmospheric CO2. This week the landmark value of 400 ppm was reached, which is a significant amount more than the pre-industrial baseline level of about 280 ppm. As an elected official, it seems appropriate for you to make a public note using any of your usual outlets that this important event has occurred, in order to bring more focus to the national and regional discussion of climate change.

Here is a link to the NOAA web site giving the details:

Thank you very much,

[your name here]


  1. #1 Joseph A. Marcus
    Cambridge, Massachusetts
    May 11, 2013

    Greg, thank you for providing the NOAA link. Yesterday, The Guardian blogger George Monbiot characterized 400 ppm of atmospheric CO2 as a monumental way station on [our doomed civilization’s] “road of idiocy.” A road he calls “the Via Dolorosa of environmental destruction” – which strikes me as an interesting metaphorical use of powerful Christian imagery:
    Thanks again,
    Joe M.

  2. #2 Lars Karlsson
    May 12, 2013

    “Benchmark” seems lika s strange choice of word. Do you mean “landmark”, or “milestone”?

  3. #3 Greg Laden
    May 13, 2013

    A benchmark is a reference point. We’ve been using the 400 ppm reference point for years. It is a perfectly good word. But for some reason a few people have complained to me about this word choice. I think maybe there are other aspects of this story that are more important, don’t you think?