Global Warming 101

Climate scientists have not been sitting on their thumbs for the last 25 years.

There just aren't that many potential causes of the present global warming trend.

It's either caused by more heat coming in to the atmosphere or less heat coming out.

If it's an increase in heat going into the system, then the possible sources are:
# increased insolation
# increased geothermal
# increased anthropogenic heat

All of these have been studied extensively and any increase in heat entering the system cannot account for the present global warming.

Thus less heat is coming out, which can be caused by:
# decrease in planetary albedo
# increase in greenhouse gases

Again, these have been extensively studied.

Change in planetary albedo does not explain current global warming, although pretty much all of the decrease is anthropogenic.

So we're left with greenhouse gases.

And in fact we find that greenhouse gas concentrations have skyrocketed.

And if we separate natural and anthropogenic greenhouse gas contributions we find that the increases in greenhouse gases are primarily anthropogenic.

It's certainly a lot of work to eliminate the other possibilities, but that work has been done.

* The 2001 IPCC report estimates of global mean forcing from the different elements (greenhouse gases, solar, etc.)

* The overall anthropogenic growth in greenhouse gases.

For example, CO2 grew from 278 to 265 parts per million between 1750 and 1998. Methane grew from 700 to 1745 parts per billion.

* Breakdown by sector of greenhouse gas emissions

Sources of CO2 Emissions

* What is known about the potential for, and costs and benefits of, and time frame for reducing greenhouse gas emissions?

Significant technological and biological potential exists for near-term mitigation. Forests, agricultural lands, and other terrestrial ecosystems offer significant carbon mitigation potential. Conservation and sequestration of carbon, although not necessarily permanent, may allow time for other options to be further developed and implemented. Adoption of opportunities including greenhouse gas-reducing technologies and measures may require overcoming barriers through the implementation of policy measures.  The successful implementation of greenhouse gas mitigation options would need to overcome technical, economic, political, cultural, social, behavioral, and/or institutional barriers that prevent the full exploitation of the technological, economic, and social opportunities of these mitigation options. Coordinated actions among countries and sectors may help to reduce mitigation cost by addressing competitiveness concerns, potential conflicts with international trade rules, and carbon leakage. A group of countries that wants to limit its collective greenhouse gas emissions could agree to implement well-designed international instruments.

* 2001 Summary of Settled Knowledge and Open Questions

For example, settled knowledge six years ago:

Most of observed warming over last 50 years likely due to increases in greenhouse gas concentrations due to human activities.

Open question six years ago:

Relating regional trends to anthropogenic climate change.

It will be highly instructive to compare this table with the equivalent one from the new report.

Tags: Global Warming, IPCC (all tags)


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