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For Immediate Release, June 5, 2008


Kieran Suckling, Executive Director
(520) 275-5960,

Kassie Siegel, Climate, Air and Energy Program Director
(760) 366-2232 x 302, (951) 961-7972 (cell),

Bill Snape, Senior Counsel
(202) 536-9351,

Lieberman-Warner Climate Security Act Is Substantially Inadequate

Atmospheric Carbon Target Falls Far Short of 350 ppm;
Will Not Save the Polar Bear, Reverse Arctic Melting Trend, or Prevent
Catastrophic Runaway Global Warming

WASHINGTON, D.C. Global warming is the greatest collective threat humanity has ever faced. Atmospheric carbon dioxide and methane levels have soared well beyond any previous high of the past 800,000 years. The current atmospheric carbon dioxide level of 385 parts per million (ppm) has already exceeded the maximum safe level of 350 ppm [1]. If the carbon level is not immediately and dramatically reduced, natural tipping points will likely be triggered, causing runaway warming outside of human control. Recent spikes in methane, ocean acidification, and Arctic melting that exceed those predicted by scientific models are initial indications that dangerous positive feedback loops may already have been triggered [2].

The acceleration of Arctic sea-ice melt is of special concern because of its threat to polar bears and because the Arctic has long been identified as a likely global tipping point. Sea ice reflects the Sun’s energy back to space, cooling the planet. When the ice is replaced by water — which absorbs the Sun’s energy — Arctic warming accelerates rapidly. Additionally, massive methane reservoirs currently locked in the frozen tundra are released, further exacerbating global warming. The net effect is to switch the Arctic from a planetary cooling to a planetary warming mechanism. If the Arctic’s energy balance is not restored very soon, the Greenland ice sheet may be put on an irreversible melting trajectory that would raise global sea levels by approximately 20 feet.

We agree with the conclusion of NASA’s James Hansen:

“Present policies, with continued construction of coal-fired power plants without CO 2 capture, suggest that decision-makers do not appreciate the gravity of the situation. We must begin to move now toward the era beyond fossil fuels. Continued growth of greenhouse gas emissions, for just another decade, practically eliminates the possibility of near-term return of atmospheric composition beneath the tipping level for catastrophic effects… [I]f the world continues on a business-as-usual path for even another decade without initiating phase-out of unconstrained coal use, prospects for avoiding a dangerously large, extended overshoot of the 350 ppm level will be dim.” [1]

Any greenhouse gas regulation bill that does not 1) prescribe emission levels that will reduce atmospheric carbon to 350 ppm, 2) prioritize reductions in methane and black carbon emissions, 3) ensure the reversal of Arctic melting to avoid a planetary tipping, 4) prohibit the construction of new, and phase out existing, non-CO 2-capturing coal-fired power plants, and 5) save the polar bear from extinction, will not solve the global warming crisis.

The Lieberman-Warner Climate Security Act (CSA), in its original and substitute form, represents a substantial effort to shift the United States toward a low-carbon economy while developing and funding strategies to allow ecosystems and human communities to adapt to unavoidable warming impacts. The current form includes important new protections for plants, wildlife, and endangered species.

Unfortunately, however, the CSA meets none of the criteria for an adequate greenhouse gas bill.  If all of its goals are met (and none its loopholes activated), the CSA will reduce total U.S. emissions by only 66 percent below the 2005 level [3]. The bill’s authors and the Environmental Protection Agency agree that under this scenario, atmospheric carbon levels will grow from 385 ppm to 488 ppm and remain on an increasing trajectory [4].

This level of atmospheric carbon will produce catastrophic impacts to human health and economies, wildlife, and ecosystems. It will undermine the bill’s wildlife adaptation provisions, as most wildlife will simply not be able to adapt such a world, regardless of conservation efforts. Neither Arctic summer sea-ice nor polar bears will survive under these conditions.

The Sanders-Boxer, Waxman, and Markey bills, as well as Sanders’ proposed amendment to the CSA, would deepen emission cuts to 80 to 85 percent of 2005 levels, resulting in a carbon level of approximately 450 ppm. These excellent bills need to be updated based on the newest science, which shows that the 450 ppm target will not avoid “dangerous anthropogenic interference with the climate system.” The current state of scientific knowledge indicates that carbon dioxide must be reduced to 350 ppm [1]. As the atmospheric concentration is already at 385 ppm, it is imperative that carbon emissions be cut by at least 90 percent and augmented by sequestration programs to make the United States a net carbon sink.


[1] Hansen et al. 2008. Target Atmospheric CO2: Where Should Humanity Aim?

[2] Catchpole, D. 2008. Scientists warn of rising Pacific Coast acidity. Associated Press, May 28, 2008; Black, R. 2008. Methane rise points to wetlands. British Broadcasting Service, May 23, 2008. Stroeve, J. et al. 2008.  Arctic sea ice extent plummets in 2007.  Eos 89:13-20.

[3] Boxer, Barbara. 2008. A Summary of the Boxer Substitute Amendment to the Lieberman-Warner Climate Security Act, May 16, 2008.

[4] A press release issued by Senator Lieberman on October 18, 2007 asserts that “if the U.S. achieves emissions reductions of the magnitude mandated by ACSA, then — making conservative assumptions about the pace of emissions reductions in the rest of the world — the concentration of greenhouse gases in the atmosphere will remain below 500 parts per million (ppm) at the end of this century.” A March 14, 2008 report by the Environmental Protection Agency entitled “ EPA Analysis of the Lieberman-Warner Climate Security Act of 2008” concludes that full implementation would result in an atmospheric carbon level of 488 ppm, but on an increasing trend, by 2095 (page 192). These estimates assume a related level of international action which is outside the purview of the bill.

Graph Sources

Current path: World Resources Institute. 2007. Comparison of Legislative Climate Change Targets in the 110 th Congress.

450 ppm stabilization window: Metz, B. 2007. Time for action? Options to address climate change. Netherlands Environmental Assessment Agency, Co-chairman, IPCC Working Group III. Presented in Dublin, Ireland, Nov. 27, 2007; den Elzen, M. G. J. and M. Meinshausen. 2005. Meeting the EU 2°C climate target: global and regional emission implications. Report 728001031/2005. Annex I nations reduction target calibrated to 2005.

Bills: targets as described in bills, calibrated to 2005, change between target years presumed to be linear.

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