• Visit the EPA Global Warming Site
• Lots of Sites out there
• Tropical Dams and Global Warming

What do the latest models show? Here we see the predicted temperature increases on the land surface when the data is analyzed in cumulative time slices.

Later we will compare the models with some data.

Current concentration of CO₂ is 360 ppm

Current concentration of CH₄ is 1.8 ppm or 25x1.8 = 45 ppm CO₂ equivalent. This is 12% of CO₂ concentration and its growing 2.5 times as fast.

More About Methane:

• has a nice page on methane and where it comes from, ie methanogenic bacteria
• is a table for estimated sources and sinks of methane in Tg/yr.
• Is a comprehensive site for all the greenhouse gases. It claims deforestation as an atmospheric methane source which is true.
• Methane Cycle

Time to run the simulation (not ready for public linkage yet).

Methane Removal Mechanism (some estimates suggest the methane residence time is up to 10 years so there is no short term equilibrium control):

Atmospheric Chemistry:

CH₄ + 2O₂ CO₂ + 2H₂0

OH + CH4 + 02 H2O + CH3O2

CH3O2 + NO +02 H2CO + HO2 + NO2

CH3O2 + HO2 CH3OOH + O2

H2CO + uv H2 + CO

CH3OOH +OH H2O + CH3O2a

Is this apparent reduction in the rate of methane build up due to a threshold effect that is does methane build up until the atmospheric chemistry is temporarily accelerated? Was Pinatubo to blame?

An expert's view

Ice Core Data:

Manifestations and Predictions of the Greenhouse Effect:

An example of Myth Perpetuation: Deforestation of the Amazon Rain Forest greatly contributes to the Greenhouse effect:

Its the total amount of biomass on the planet that contributes to the Carbon Cycle . Because of agriculture, this biomass is actually increasing with time (which contributes to the methane problem).

Note - the biggest uncertainty with the whole carbon cycle is the role of deep ocean transport:

The oceans' uptake of CO2 primarily depends on how fast CO2 can be transported downwards from the ocean surface; if "too much" CO2 accumulates in the surface layers at one time, absorption slows down.

Global data on the concentrations of CO2 in the oceans are still very sketchy, and many contributing factors, such as ocean biology, are still not well understood. Absorption is also known to depend on local weather conditions. For example, winter storms accelerate CO2 exchange by exposing sea-water to the atmosphere through bubbles and spray.

Trees are temporary storage only; they fall down and rot and release Carbon eventually

Biggest problem is that the Amazon Rain Forest is a net producer of greenhouse gases rather than a net sink. That is, this environment produces a great deal of methane which is emitted by the forest and that is larger than the amount of CO₂ which is absorbed. This point is a bit controversial still, however.

The Amazon Rain Forest should be preserved as a species habitat; arguments to preserve it to "reverse" the Greenhouse effect are incorrect and demonstrate that people don't know about methane production and its effects.

Simplest Prediction is increase in global mean temperature. Can We see evidence for this in the Data?

Role of clouds is crucial --> Net Cooling or Warming? --> There is general consensus that cloud cover will increase as the capacity for the atmosphere to retain water increases with increasing temperature.

What does the actual data look like?

All the Data: Global Warming NCDC Document

Long Term Temperature Trends:

• Northern Hemisphere Temperature Trends:

  

• Southern Hemisphere Temperature Trends:

  

• World Temperature Trends:

  

• Summary of Data:

  

Potential Problems:

• Is the pre-1920 data reliable?
• Increasing number of recording stations since 1950 means non-uniform data quality
• Southern Hemisphere is more ocean to land area than Northern Hemisphere
• But, there does appear to be an 0.5 degree Celsius increase per century in the data

Distribution of Temperature trends on the Earth. Where is it getting warmest the fastest:

All the historical data

1953-1973:

1973-1993:

When positional data is combined with temperature data and timesliced in this way - it seems clear the Global Warming is occurring. This conclusion was reached by a National Academcy of Science panel in Sept. 1995 and is accepted by most.

Temperature Variations with Altitude

What about the US:

Annual US Trends

Max Temperature US Trends

Min Tempearture US Trends

Annual Precipitation Trends

Number of Tornadoes

Some Conclusions

Evidence of increased hurricane strength is here: Hurricane Andrew ; Elmira in the Pacific

Some Additional Internet Resources:

Public Perception on Global Warming

Nice Overview

Technical Data on Gas Concentrations and Growth with time

Add your questions or comments about this particular lecture

Previous Lecture Next Lecture Course Page