U.S. Climate Bill Unlocks Path to Preventing Dangerous Global Warming

One of the chief talking points of opponents of US clean energy and climate legislation is the claim that the bills working their way through Congress would have little impact on global warming.  Taking US action in isolation, they claim that reducing US emissions won't make much of a dent in world emissions and future temperature increases.  After all, we account for only about 20% of the world's emissions. 

But the US is more than just a bit player in this piece.  There's an old saying in American politics:  "As goes Maine, so goes the nation."  When it comes to solving global warming, it's "As goes the US, so goes the world." 

The recent analysis of the Senate climate bill by the US Environmental Protection Agency (EPA) (available here) provides a better look at this issue than the EPA's previous analysis and reflects more recent developments from key players.  Here, EPA analyzed the case where other countries join the US in taking aggressive action to address global warming.

These aren't made up scenarios.  The actions that EPA posits that these countries undertake are in line with the commitments developed countries made at the most recent meeting of the Group of Eight (as I discussed here) and the actions developing countries have recently announced (as I discussed here and here).

So what did EPA actually analyze?  They analyzed a scenario where the:

  • US undertakes emissions cuts in line with the climate bills targets;
  • Developed countries emissions take annual emissions cuts until their emissions are 83% below 2005 levels in 2050 (the same emissions path as the US climate bill and their G8 commitments);
  • Developing countries adopt a policy beginning in 2025 that caps emissions at 2015 levels, and linearly reduces emissions to 26% below 2005 levels by 2050; and
  • The combination of U.S., developed, and developing country actions limits emissions in 2050 at 50% below 2005 levels.

Is this a realistic scenario?  Some people would say "yes" because if the US leads, others will follow.  Other people would say "yes" because if others lead, the US will follow.  Whichever way you think the arrow of leadership points, the one scenario that is pretty unlikely is that the US is the only one to act.  In fact, it's much more likely that the US would be the only one not to act.

And the actual steps that each country undertakes in EPA's analysis aren't far fetched.  They are in line with the level of global effort that we are trying to achieve and that is the basis of the international negotiations -- deep cuts in the emissions of developed countries and sizeable cuts from developing countries in the medium-term.  This level of global action -- partly spurred by US action to address its emissions -- leads to significant cuts in global warming pollution around the world (as you can see from this figure using data from the EPA analysis where the line labeled "G8" is the actions taken by these countries and the line labeled reference is where they would head without these actions).

This scale of action would hold global emissions to a level called for by scientists and world leaders (see here and here) - namely 3.6°F (2°C) above pre-industrial levels or 450 parts per million.  We will suffer impacts from global warming even at this level.  But they will become especially severe in a number of regions around the world, including the US, if we cross this threshold.

As this figure from the EPA analysis shows, under a mid-range climate sensitivity (the group of bars called CS=3), global temperatures would stay below 3.6°F (2°C) when US action helps spur the global action discussed above -- developed countries taking targets in line with what they have already committed to and developing countries making serious efforts in the mid-term (under the scenario called G-8 - International Assumptions -- the blue bar).


What, you say, the US's action leads other countries to also take action?  Yes, that is exactly what will likely occur as the US is a key player in global efforts.  Which is why groups with as diverse a membership as the US Climate Action Partnership have stressed:

"strong, credible action by the U.S. is a critical first step to encourage action by developing countries."

But even if you believe the alternative "arrow of leadership", US action won't happen in isolation.  And US action will have a large impact in helping ensure that the types of actions from other key countries actually occur.  

So as the Senate begins its deliberation of a clean energy and global warming bill, don't believe it when you hear the claim that the bill will have no impact in addressing global emissions or keeping temperatures below critical thresholds.

Enactment of a US climate bill with strong limits on our emissions (that passes the 2 billon ton test as my colleague discussed here and here) and that provides important tools for US climate negotiators (as I've discussed here and here) will help unlock global efforts and move the world closer to solving this challenge.

A reasonable person would have to conclude that efforts by the world's largest economy will spur global efforts.  Anything less just wouldn't be based on the facts and would underestimate the influence that the US has around the world!


Thanks to my colleagues David Doniger and Dan Lashof for their helpful input.