Climate petitions and open letters

I've been collecting details on some of the many petition drives and open letters issued over the past several years related to climate change. I've divided these into two categories: the scientific case for action, and broader calls from the general public.

The scientific case for action

Is there strong evidence that human activity is changing the composition of the atmosphere? How strong is the greenhouse effect from CO2, methane, and other human-generated GHGs? How much higher would CO2 levels rise under "business as usual?" How much would temperatures be likely to rise in that case? How far will we need to cut emissions and concentrations to keep temperature increases to a specific level?
These are scientific questions, where public opinion ought to defer to the expertise of those who spend their lives researching these questions. We can ask for an explanation in layman's terms, and inquire whether the scientists are confident in the results, how widely accepted the conclusions are, and what issues are still up for debate, but we can't ask to vote on whether CO2 is a greenhouse gas. On these issues, the scientific literature gets the final say.
Since this is a vast subject, we do need it to be 'boiled down' to some yes-or-no conclusions for the public and political leaders to use. That has been the mandate of the IPCC in their Assessment Reports. These reports have then been reviewed and endorsed by major associations of scientists including many national academies of science. The U.S. National Academies of Science further conducted its own assessment reports.

Surveys of Scientists

There have also been a number of attempts to poll climate scientists for a very brief and simple take on their views; the results have been highly variable, with issues around choice and wording of questions, as well as selection of participants.

Open Letters from Scientists

As for calls to action (or otherwise) in response to the science, we have a number of open letters written and endorsed by scientists themselves. These should be judged on the relevant expertise of the signers. I have more information on a large number of individual scholars, their academic affiliation, and their publication record in my pages on climate scientists. I've been adding notes on who signed which of these open letters in the 'notes' column of my tables. Some of the major open letters from scientists:

Letters from 'Skeptics'

Those who question the entire scientific basis for any call to cut greenhouse emissions have also been active in writing and endorsing open letters and declarations. I've located the following of these, and added notations of who signed which of these in the notes column of my tables, using the abbreviated tag shown in bold by each item:

How to respond

There is plenty to debate here: whether GHG cuts should be rapid or gradual, whether to use carbon taxes or cap-and-trade, which countries should bear what share of the burden, what types of technologies and strategies should be pursued, etc. Here, engineers, economists and social scientists have some bearing as expert sources; but in the end these policy choices need to win consent from the general public. Everyone can and should have a say in these discussions, through the electoral process, via community groups and NGOs, in online discussions, petitions, etc.


On economics, one recent statement from 152 global institutional investors with over $9 trillion in assets was delivered at the Poznan climate talks in Dec. 2008. The statement was issued by: It states:
"Clear, credible long-term policy signals are critical for investors to integrate climate change considerations into their decision-making processes and to support investment flows into a low-carbon economy and into measures for adaptation. A timely post-2012 climate change agreement involving all countries and containing appropriate long- and medium-term emission reduction targets is essential to supporting investor confidence. The global agreement must facilitate and encourage strong national action plans in order for us to help meet the climate challenge."

Public petitions

There have been several major petitions calling for action on cutting greenhouse gas emissions. Those are by far the largest petitions. Other petition drives have reached into five figures, including: