Geography 2412 Lecture Notes 11/13

 

Global Climate Change (aka global warming)

Chap 4: pp. 132-150

 

The simple physics:  This is all about the radiation balance of the earth, and thus its climate. The balance is determined by solar radiation (short wave) coming in minus reflection and terrestrial (long wave) radiation going out. A set of gases have “greenhouse” qualities: they are relatively transparent to short wave radiation and relatively opaque to long wave. These are especially (in the earth’ atmosphere) water vapor, carbon dioxide, ozone, methane, and some synthetic gases like CFCs (chloroflourocarbons like refrigerants such as Freon).

 

Humans are increasing CO2 and methane (both also come form natural sources). CO2 comes mostly from burning of fossil fuels and de-forestation (or other activities that degrade vegetaiton, which when it decomposes oxidates and releases the CO2 it gathered when it grew thru photosynthesis). Methane comes from agriculture and our extraction of natural gas from the earth’s crust.

 

The earth would be cold (like Mars) if not for greenhouse effect, but question is whether the

Human enhancement of the effect can actually change the radiation, and thus the temperature and climate of the earth.

 

And global mean temp has risen since the late 1800s, when industrialization really kicked up greenhouse gas concentrations. There rmains some uncertainty about this, whether the warming is really caused by human-enhanced CO2, but a wide scientific consensus has formed that current global warming is anthropogenic.

 

The great question is what will happen with continued greenhouse enhancement?

Lots of uncertainty:

  1. the models used to predict global climate change are limited in accuracy
  2. other factor (volcanoes, etc.) could have affected the historical warming and make the future uncertain
  3. the future carbon content of the atmosphere is uncertain: how many people, usng how much fossil fuel? How much carbon will remain the atmosphere vs sink into oceans and bio-mass?
  4. What feedbacks might be negative, that is, they dampen the effect: clouds cool the earth, and may be more extensive as warming occurs and intensifies the hydrological cycle (a negative feedback); a warmer, CO2 enriched atmosphere should make plants grow btter, so bio-mass might absorb more carbon;

 

Some effects seem pretty certain (pp. 138-139):

 

  1. Overall warming: maybe 1.5 to 5.0 C, in next 100 years
  2. Overall wetter: warmer conditions mean more evaporation and precipitation overall, though some regions may get drier.
  3. (Indeed) many models predict that the mid-latitude continental areas will get drier, especially in summer. This could mean more droughts.
  4. Sea level rise: hard to avoid in a warmer world as glaciers melt and warmer ocean water expands

 

Social Impacts (p. 140):

  1. Disrupted agriculture  (especially low latitudes, with potential expansion of ag in higher latitudes), could reduce food security
  2. Reduced water supplies (especially in mid-latitudes)
  3. Coastal flooding and big land use impacts along coasts

 

Policy Responses

 

  1. Mitigation: reduce the build-up of greenhouse gases in the atmosphere (this requires formal international governmental action, and mostly means altered energy systems)
  2. Adaptation: get ready for climate change and variability (this would be the neo-classical view: let markets respond as needed rather than step in  with government regulation)
  3. Geo-engineering: tinker with global radiation balance or bio-geochemcical cycles (table 4.3)

 

Policy responses must be global, multilateral, thus they are inherently difficult

 

Must address equity of cause/impacts

 

International Mitigation Agreements

 

Rio Accord (1992): voluntary reductions in GHGs

Kyoto Protocol (1997): industrial countries reduce GHG collectively by 5% below 1990

Arguments over “targets and time-tables”

 

Harper’s criticisms p. 148):

 

Weak agreement (not sufficient to stem the problem anyhow)

Flexibility and loopholes (MDCs sought loopholes, like carbon sequestering credits)

“hot air” Trading (allows countries that more readily meet targets to sell their carbon credit (difference between target and what they actually emit) to those having more trouble—this does not reduce GHG

Ratification trap (55% o MDC emissions, w/.o US, the single biggest emitter of GHGs) but oher mDCs don’t want to leave out the US, which has decided not to ratify the Climate Convention and follow Kyoto Protocol—thus having something like veto power over.

 

Bush’s criticisms: (see recitation manual)

 

Kyoto and climate convention it implements are “Flawed” (no really long term goals, inadequate science)

Gives LDCs a pass

Not based on science

Too “precipitous” (US 7% is actually 30% given growth by 2008-2012)

Hurts the US economy

Makes US depend on uncertain emissions trading

 

Options?

 

Re-negotiate to involve LDCs in earlier reductions?

Improve terms of technology transfer? Can more rapid development solve the problem?

Accept more GW but expect post-development reductions (say starting in 2050 or later?)

Go for more Carbon sequestering/Geo-engineering? Go for adaptation? Wait and see?