The National Wildlife Federation's blogger says Lieberman-Warner is "a really strong bill" that "falls just short" of their goal "of an 80% cut in carbon emissions by 2050." When I point out that L-W only achieves about a 60% cut, NWF responds:
80% cuts in carbon emissions will save the planet.
60% cuts in carbon emissions will destroy the planet.
How does that logic work?
Notwithstanding the fact I never said anything of the sort, here for your reading pleasure is the difference between the targets in Lieberman-Warner and the targets recommended by the NWF itself.
If the U.S. and other industrialized nations achieve reductions of 25-40% by 2020 and 80-95% by 2050, we have a good shot of limiting long-term warming to 2°C above pre-industrial levels.
If, instead, the U.S. achieves only the L-W targets, we will be committing ourselves to long-term warming of at least 2-4°C, which will have many unavoidable catastrophic effects, such as widespread to mass extinction (which one would think the NWF would care about).
This is explained (with tables and charts) below the jump.
The IPCC reports are quite clear, once you add them up. We need to start with the emission targets in Lieberman-Warner and find out what the science says they would likely leave us with in terms of impacts.
MATCHING EMISSION REDUCTION TARGETS TO STABILIZATION SCENARIOS
The first question is how the caps ("emissions reduction targets") affect the concentrations of greenhouse gases in the atmophere (the "stabilization scenarios").
Let's start with Box 13.7 in the 4AR (WG3).
The U.S. is an Annex I country. Lieberman-Warner (a 0% reduction by 2020 and a 60% reduction by 2050) puts us in Scenario C (650 ppm CO2-equivalent).
Since the rest of the Annex I countries are shooting for reductions matching Scenario A numbers (see Europe's pledge and the non-US Bali agreement), even with the U.S.'s intransigence we might luckily end up in Scenario B (550 ppm CO2-equivalent).
Scenario category | Region | 2020 | 2050 |
---|
A-450 ppm CO2-eq | Annex I | –25% to –40% | –80% to –95% |
Non-Annex I | Substantial deviation from baseline in Latin America, Middle East, East Asia and Centrally-Planned Asia | Substantial deviation from baseline in all regions |
B-550 ppm CO2-eq | Annex I | -10% to -30% | -40% to -90% |
Non-Annex I | Deviation from baseline in Latin America and Middle East, East Asia | Deviation from baseline in most regions, especially in Latin America and Middle East |
C-650 ppm CO2-eq | Annex I | 0% to -25% | -30% to -80% |
Non-Annex I | Baseline | Deviation from baseline in Latin America and Middle East, East Asia |
DIFFERENCES BETWEEN STABILIZATION SCENARIOS
So now the question is what are the likely consequences of committing to global CO2eq. concentrations of 550-650 ppm instead of 450 ppm?
At those levels we're very likely committed to 2°C-4°C warming above pre-industrial levels (see below), with a reasonable likelihood of up to 6°C warming.
Figure SPM.8 in the 4AR WG3 Summary for Policymakers:
IMPACTS
Why do scientists agree that 2°C warming should be avoided? One can read through the reports (like Table 19.1 of 4AR (WG2)), but the Wikipedia articles on the Avoiding Dangerous Climate Change Symposium in 2005 (already dangerously outdated), and The effects of global warming is a useful start.
Here's a quote from the 4AR Summary for Policymakers that may be of interest to the National Wildlife Foundation:
There is medium confidence that approximately 20-30% of species assessed so far are likely to be at increased risk of extinction if increases in global average warming exceed 1.5-2.5°C (relative to 1980-1999). As global average temperature increase exceeds about 3.5°C, model projections suggest significant extinctions (40-70% of species assessed) around the globe.
Since 1980-1999 temperatures were 0.5°C above pre-industrial levels, that means that in pre-industrial terms:
There is medium confidence that approximately 20-30% of species assessed so far are likely to be at increased risk of extinction if increases in global average warming exceed 2.0-3.0°C (relative to pre-industrial levels). As global average temperature increase exceeds about 4.0°C, model projections suggest significant extinctions (40-70% of species assessed) around the globe.
So, yes, there is a significant difference between 80% reductions and 60% reductions in GHG emissions.