Caldeira Lab Research:Energy, Global Carbon Cycle, and Climate

Stabilizing climate requires near zero emissions

H. Damon Matthews & Ken Caldeira

Even if human carbon emission was stopped now and greenhouse gas levels were stabilized in the atmosphere, the climate would continue to warm for centuries following. To fully stabilize the climate, CO2 emissions will need be tightly regulated not only now but for hundreds of years. In fact, it is shown here that in order to bring our climate back to normal, CO2 emissions must be nearly eliminated for several centuries.

Matthews, HD; Caldeira, K, 2008. Stabilizing climate requires near-zero emissions, Geophysical Research Letters 35 (4), DOI: 10.1029/2007GL032388

Atmospheric consequences of a single pulse of carbon: In the model, a single pulse of carbon in amounts ranging from 50 to 2000 gigatons was added to the atmosphere. The single pulse was followed by a 500 year period without emissions. Even when lacking additional emissions, the temperature rise induced by the pulse was not reduced significantly over the 500 year length of the model.

Effects of continued carbon emissions followed by stabilization: Along with the effects of a single pulse of carbon dioxide, the model also modeled climate change caused by steady emissions until 2050 followed by stabilization at various concentrations. After stabilization, emissions were reduced to zero. Following the end of emissions, climate change continued.


Current international climate mitigation efforts aim to stabilize levels of greenhouse gases in the atmosphere. However, human-induced climate warming will continue for many centuries, even after atmospheric CO2 levels are stabilized. In this paper, we assess the CO2 emissions requirements for global temperature stabilization within the next several centuries, using an Earth system model of intermediate complexity. We show first that a single pulse of carbon released into the atmosphere increases globally averaged surface temperature by an amount that remains approximately constant for several centuries, even in the absence of additional emissions. We then show that to hold climate constant at a given global temperature requires near-zero future carbon emissions. Our results suggest that future anthropogenic emissions would need to be eliminated in order to stabilize global-mean temperatures. As a consequence, any future anthropogenic emissions will commit the climate system to warming that is essentially irreversible on centennial timescales.