Giving up on 1.5˚C?

The climate plan released yesterday by House Select Committee on the Climate Crisis is a thoughtful, detailed plan. But it is not a plan for limiting global warming to 1.5˚C. The plan just doesn’t cut carbon pollution fast enough.

The final global temperature we reach depends on the total carbon pollution emitted between today and the day that global emissions finally reach zero (or net zero).

So, near-term carbon emissions (and reductions) matter. Limiting warming to 1.5˚C is not just about the date by which zero emissions is finally reached.

In the near-term, the House Select Committee plan would reduce U.S. emissions 37% by 2030. The very top of the official 4-page summary highlights this statement “The non-partisan think tank Energy Innovation modeled a subset of these recommendations and found the Climate Crisis Action Plan would: Reduce net U.S. greenhouse gas emissions by at least 37% below 2010 levels in 2030 & 88% below 2010 levels in 2050; the remaining 12% of emissions are from the hardest-to-decarbonize sectors (heavy-duty & off-road transportation, industry, & agriculture). There is no other statement in the summary on the national short-term goal, though the full report calls on the President to set a 2030 goal.

However, to limit warming to 1.5˚, the IPCC finds that the GLOBAL average CO2 reduction by 2030 should be 45% (and net zero by 2050.)

So, for the House Committee plan to be considered in line with a global effort to limit warming to 1.5˚C, one has to assume that other countries are going to reduce their emissions much faster than the U.S.over the near-term.

However, the opposite dynamic is actually required under the formal terms of the UNFCCC treaty — a treaty ratified by the U.S. Senate. Under the terms of the treaty, the U.S. has both the capacity and the responsibility to move MUCH faster than the global average.

Perhaps more importantly, realpolitik tells us that the rest of the world is extremely unlikely to follow the 1.5˚ path if the U.S. isn’t going down that path.

This is probably the single biggest reason that the House Select Committee plan isn’t a 1.5˚ plan.

But there’s more.

The House Select committee uses 2010 as the baseline year for comparing the modeled results of their plan to the IPCC 2030 global goal, and this approach has the knock-on effect of lowering the implied reduction effort required from the U.S. in the global effort to limit warming to 1.5˚C.

The IPCC used 2010 as a baseline year for the global effort, by expressing the required reduction in 2030 as a share of the emissions level back in in 2010 — as opposed to expressing the emissions required in total tons. From a public communications perspective, this makes a lot of sense as almost nobody has any idea how many gigatons of CO2 pollution are currently going up in smokestacks. And expressing the global effort as as reduction from any one particular baseline year is a straight forward proposition. But this does not extend to the national level. Different countries have been on very different emission trajectories up to and after 2010. Translating this baseline year approach to the national level for individual countries has all sorts of implications the IPCC did not intend.

The IPCC goal for reducing emissions 45% by 2030 is referenced to the level of emissions in the year 2010 — i.e. by 2030 emissions need to be 45% lower than they were back in 2010. However, global emissions have risen a lot since 2010, so the reduction required from today’s level is significantly higher than 45%. The choice of baselines doesn’t matter when taking a global view, as the total number of tons to be reduced by 2030 remains the same. However, it matters a lot, when taking a national view. In the U.S. emissions actually fell between 2010 and today. So, if one uses a 2010 baselines for calculating a 45% emissions reduction by 2030, it means assuming that the U.S. is a bit of the way there already, while the rest of the world has walked backwards. And this assumption implies that the U.S. has to do less than the rest of the world. But that’s not how the IPCC intended the baseline to be used. That baseline was meant for referencing global action only. The methodology for breaking out national shares without referencing 2010 national levels is complicated, but doable.

Finally, the House Select Committee apparently assumes that the U.S. should aim for reductions commensurate to the global average (while setting out a plan that has the U.S. actually lagging behind the global average). That’s not how the most of the rest of the world views the situation. Looking at the U.S. responsibility for emissions back to 1950 many advocates calculate that the US fair share of the global mitigation effort in 2030 is equivalent to a reduction of 195% below its 2005 emissions levels.

This number is so eye-popping because we long ago ate up way more than our share of the global carbon budget. Obviously that kind of reduction is impossible unless the U.S. makes a massive effort overseas, helping developing countries to grow on the clean path. But this Committee plan doesn’t provide anywhere near that kind of international effort. For context, the total Sanders Green New Deal plan (including domestic and international action) aimed for the equivalent of 161% reduction by 2030.

Taken altogether, it’s clear that that while the House Select Committee has put together a detailed, well-thought out plan, the House Committee plan is not a 1.5˚C plan.

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P.S. On Jul 2, I edited this post to clarify that while the House Select Committee plan would reduce U.S. emissions 37% by 2030, that is not an explicit goal of the plan, rather the plan calls upon the President to set the 2030 goal. I have struck the discussion of 2050 goals as the House Committee plan aims reach net-zero for CO2 emissions, offsetting remaining CO2 emissions through forestry. Further I have expanded the discussion of IPCC baseline years — an extremely complicated topic.