Preventing Dangerous Climate Change

Session 10Neil LearyChanging Planet Study GroupJuly 19-22, 2010

Cooling the Liberal Arts CurriculumA NASA-GCCE Funded Project

Photo: Roger Braithwaite, University of Manchester

Ultimate objective of UNFCCC

• Article 2: “The ultimate objective of this Convention . . .

stabilization of greenhouse gas concentrations . . . at a level that would prevent dangerous

anthropogenic interference with the climate system.”

Source: IPCC 2007 WG2, Table 20.8

Greenland Mass Loss – From Gravity Satellite

Slide from J. Hansen’s presentation to National Press Club, June 2008

Probability of overshooting 2°C (stabilisation)Meinshausen, 2005, Scientific Symposium on Avoiding Dangerous Climate Change,

Exeter, UK

Jim Hansen: must aim even lower

Slide from J. Hansen’s presentation to National Press Club, June 2008

Hansen’s prescription for 350 target

1. Phase Out Coal CO2 Emissions- by 2025/2030 developed/developing countries

2. Rising Carbon Price- discourages unconventional fossil fuels & extraction of every last drop of oil (Arctic, etc.)

3. Soil & Biosphere CO2 Sequestration- improved farming & forestry practices

4. Reduce non-CO2 Forcings- reduce CH4, O3, trace gases, black soot

Slide from J. Hansen’s presentation to National Press Club, June 2008

Scenarios assume no “Other” = Tar Sands, Oil Shale, Methane Hydrates

Coal phase-out by 2030 peak CO2 ~400-425 ppm, depending on oil/gas.

Faster return below 350 ppm requires additional actionsSource: Hansen et al., Target atmospheric CO2: where should humanity aim? Open Atmos. Sci. J., 2, 217-231, 2008.

The Effect of Delay (same risk of overshooting)Meinshausen, 2005

How hard will it be?

Small Groups

A. What is dangerous?B. What do we fear? What do we value?C. Can dangerous climate change be prevented?D. Is climate change the most pressing danger?

Report back:• 2 things your students need to learn• How will they learn them?

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Essential principles of preventing dangerous climate change (Or: what should our students learn?)

• Science alone cannot determine what is dangerous– Different ethical, cultural, economic,

ideological lenses lead to different answers– Attitudes about intragenerational and

intergenerational equity– Attitudes about risk– Others are making the choice for you

• No amount of human caused climate change is risk free – Some ecosystems, species already

threatened– Small islands, low lying coasts, others already

threatened– Most systems, places not threatened yet

• Some societies are resilient, capable of adapting to significant changes– Others not– LDCs highly vulnerable– The poor, marginalized highly vulnerable– They have little responsibility for causing

climate change

• Many ecosystems will undergo substantial change– Some ecosystem types will disappear– Some species will go extinct

• Climate and other Earth systems are complex, nonlinear, chaotic– Can change abruptly– Can change in surprising ways– Poking a beast with a stick

• Potential ‘tipping points’ in:– Ice sheet dynamics & sea level rise– Ocean circulation– Monsoon systems– Permafrost; Amazon– Methane hydrates

• Stabilizing GHG concentrations is challenging, costly– 350-450 ppm extremely challenging– 50-85% emission reductions– But feasible?

• Delay can be costly– And dangerous

Useful resources

• “The Copenhagen Diagnosis,” Allison et al, 2009. Update of science since IPCC 2007 report, with focus on ‘dangerous’ climate change

• Jim Hansen’s website: www.columbia.edu/~jeh1/. Access his papers and presentations.

• “How to avoid dangerous climate change,” Luers et al, 2007, report from UCS.

• Schneider et al, 2010. Climate Change Science and Policy. Island Press.

https://gcce.larc.nasa.gov/