U.S. Climate Assessment - Grasping the Nettle Of Emissions Reductions

President Obama and German Chancellor Angela Merkel

President Obama just released the third U.S. National Climate Assessement report. The 800-page report, which has a shorter summary, carries an urgent message about the dangers posed by climate change and how policy makers and citizens in different regions of the U.S. can respond.

In the two-minute video (below) accompanying the report's release, Dr. John Holdren, Assistant to the President for Science & Technology, says this is the "most comprehensive and authoritative report ever" on the state of the climate in the U.S. and gives examples of many ways that global warming's impact is already being felt:

The contents confirm that climate change is not a distant threat. It is affecting the American people already.

A key chapter is on on how the U.S. intends to reduce its emissions.

As the IPCC did in its climate assessment, the report uses the language of carbon budgets (note: the IPCC video uses carbon, and the U.S. budget is based on C02 emissions).

To meet the lower emissions scenario (B1) used in this assessment, global mitigation actions would need to limit global carbon dioxide emissions to a peak of around 44 billion tons per year within the next 25 years and decline thereafter. In 2011, global emissions were around 34 billion tons, and have been rising by about 0.9 billion tons per year for the past decade. Therefore, the world is on a path to exceed 44 billion tons per year within a decade.

How to turn the Titanic around? How to get a 50% reduction in GHGs by 2050? What is the "strenuous action by all major emitters" that the report says is required?

Both voluntary activities and a variety of policies and measures that lower emissions are currently in place at federal, state, and local levels in the United States, even though there is no comprehensive national climate legislation. Over the remainder of this century, aggressive and sustained greenhouse gas emission reductions by the United States and by other nations would be needed to reduce global emissions to a level consistent with the lower scenario (B1) analyzed in this assessment.

Of course, this is not just a U.S. issue, although the large economies of the U.S. and China will have huge sway over the rest of the world on how the "early and large reductions in global emissions" can occur:

Achieving the B1 emissions path would require substantial decarbonization of the global economy by the end of this century, implying a fundamental transformation of the global energy system.

Not to belittle the efforts of individuals and companies who are trying to reduce their own emissions, and the importance of their actions in creating a cultural change that precedes political action, but there will need to be more than voluntary measures to encourage people to slow green house gas emissions growth.

The report lays out ways that Obama has used regulations like fuel economy standards for cars and trucks to lower emissions and the forthcoming stricter regulations on power plants in the U.S..

It notes there are many initiatives, at the various levels of government, from federal to city, to regulate emissions and also to spur the growth of renewable energy and to encourage energy conservation.

But here's what the report says about pricing carbon - using market instruments like California's cap and trade program - versus using regulation to half current emissions.

Studies of price-based policies, such as a cap and trade system, indicate that a 50% reduction in emissions by 2050 could be achieved at a cost of a year or two of projected growth in gross domestic product over the period (for example, Paltsev et al. 2009; EIA 200940). However, because of differences in analysis method, and in assumptions about economic growth and technology change, cost projections vary considerably even for a policy applying price penalties. Comparisons of emissions reduction by prices versus regulations show that a regulatory approach can cost substantially more than a price-based policy.

Whether it's the stick and carrot of regulations and subsidies for clean tech and renewables or it's a straightforward polluter-pays market-based mechanism like California's Cap and Trade on a federal scale, politicans are going to need to be focused on climate change to attain the "early and large reductions" that the report calls for.

Deciding these matters will be a continuing task, and U.S. Administrations and Congress face a long series of choices about whether to take additional mitigation actions and how best to do it.

At least, in Obama, the U.S. has a leader who appears to be prepared to take this fight on.