24 Climate Change

Class 24 - Climate Change

This is a topic that everyone has heard about and most people have strong (political) opinions about. Or are totally bored with the topic. Here are a few graphics I found recently that summarize the scientific issues. The politics is a whole other mess....

Reading - Fran's recommendations:

Global Warming - The Complete Briefing (2004, 3rd edition, Cambridge University Press) by John Houghton. Authorative book written at a level for general public - but also full of numbers and charts for those wanting details.(Houghton is retired Oxford professor and ex-director of the UK Met Office, chaired a working group of the IPCC, written books on atmospheric science from popular level to grad student)
Technical Summary report of the Working Group 1 of the Intergovernmental Panel on Climate Change (IPCC 2001) - 63-page pdf of report from the world's boffins on the subject.
Climate Change - W.J. Burroughs, (2001 also Cambridge University Press). Similar to Houghton but a bit more technical. More discussion of geological and historical changes and of causes of climate change. Up to IPCC 1995 only.
The Earth System - Krump, Kasting and Crane (2nd edition, Pearson Prentice Hall). Undergraduate textbook aimed at the general education market (i.e. non-science majors). Interesting systems approach, emphasizing feedbacks.
Earth - Evolution of a Habitable World, (1999, CUP again) by Jonathan Lunine. An astrobiology textbook written by a planetary scientist. Addresses on climate change on other planets as well as Earth.

Geological - Historical - Recent Records
Models
Predictions/Implications

Most illustrations/data are from the IPCC 2001 Technical Summary.

GEOLOGICAL-HISTORICAL-RECENT RECORDS

NOTE:

Warming for past ~20,000 yrs
Last time this warm ~120,000 yrs ago
Next glacial period ~50,000 yrs hence

It's not all warming - sulphate aerosols lead to COOLING... This is in W m^-2 - remember what is absorbed by Earth is 1368/4 x (1-0.4) ~ 205 W m^-2

Effects? Look at sea level....+-100 mm = 10 cm = 0.1 meter - not very much - YET....

Is the issue the INCREASE simply or is it an issue of VARIANCE?

Here is a summary of CLIMATE CHANGE INDICATORS - with levels of confidence

ATMOSPHERE-OCEAN GLOBAL CLIMATE/CIRCULATION MODELS

Especially, don't forget the ocean currents...

FEEDBACKS - e.g. effects of clouds. Low clouds (a) increase albedo and reflect more sunlight leading to cooling and (b) are warm so radiate IR. High clouds act like thermal blanket, absorbing out-going IR and cause net warming (I said this wrong way around in class and got myself confused).

Estimates of global average temperature changes under different assumptions about changes in greenhouse
gases and clouds - comparing the full model with basic atmospheric radiation physics

Greenhouse gases	Clouds	Change from current average global surface temperature of 15 C
As now	As now	0
None	As now	–32
None	None	–21 (we knew this one...)
As now	None	4 just removing clouds has net warming (cloud cooling is greater than cloud warming)
As now	As now but + 3% high cloud	0.3 High clouds act like thermal blanket
As now	As now but + 3% low cloud	–1.0 Low clouds increase albedo, are hot (so radiate more) and have net cooling
Doubled CO2 concentration	As now (no additional otherwise as now cloud feedback)	1.2
Doubled CO2 concentration + best estimate of feedbacks	Cloud feedback included	2.5 Net CO2 warming leads to more high clouds, less low clouds - increasing warming effect

Another simple example, we know how much O2 is lost and CO2 generated for every kg of fossil fuel burned. But some of the emitted CO2 is absorbed into the ocean, some is taken up on land (e.g. by plants.

Between 1990 and 2000 the amount of CO2 in the atmosphere increased from 352 to 367 ppm rather than all the way to 382 ppm which would have happened if ~8 ppm each had not been taken up by the land and ocean

First test the model on historic/recent data - using multiple models to show consistency and not strong dependence on starting conditions. (a) NATURAL means inlcude volcanic and solar changes only - no anthropogenic. (b) Just human - no volcanoes or solar changes. (c) combined - seems to work - these boffins know what they are doing.

Then develop SCENARIOS for the future - 34 scenarios with wide range of energy, population and socio-politico-economic possibilities. These scenarios include all sorts of effects (from population growth to energy policies to numbers of cars driven by peole in china) - spanning the range of possibilities imaginable.

HUGE range in predicted CO2 emissions - but much less range in net CO2 atmospheric abundance.... again, due to some being taken up on land and in the oceans, plus feedback effects.

NOTE - Pre-Industrial level ~280ppm. Doubled CO2 between 2040 to 2070. Models differ - particularly on feedback of biological and hydrological cycles on land - but seem to be converging on agreement/accuracy year by year.

NOTE: Doubling of CO2 in atmosphere leads to

3.7 W m^-2 forcing
2-6 C rise in global temperature, depending on model.
0.5 meter rise in sea level

But the global warming is not uniform

Great if you live in northern Canada or Siberia - but pretty miserable if you live in the Sahara, or Mexico or Australia.

For 0.77 meter in sea level increase contributions are:

0.43 m of thermal expansion of oceans
0.23 m of glacial melt
0.09 m of Greenland melt
0.02 m of Antarctic melt

This does not seem very much - especially sitting here in Boulder. But critical to those who live/farm within ~1 meter of sea level this is disasterous

30 million in China
15 million in Bangladesh
7 million in Egypt
many pacific islands - e.g. Maldives

Overrated:

Earth,Venus, Mars analogy for anthropogenic global warming
chaos theory - important for weather, maybe but not for climate
wind as alternative source of energy - takes up too much space, has other climate impacts
hydrogen economy - 30+ years

Underrated:

effects of sulphate aerosols on cooling (but acid rain!)
energy conservation
population
solar power
sequestration
threats to biodiversity

It's the ECONOMY, S@#$%^!

The end of oil is coming! Left is discovery of US oil - production peaked around 1970-ish - predicted by Hubbert in 1956 - discovery had ground almost to a halt by the 50s. Same is now happening world wide - discovery is slowing down and production seems to be levelling off. I think that in the current political hooha we are seeing the death throws of the oil industry.

Here is an optimistic approach that shows what happens if there is a dramatic drop in per capita CO2 emissions over the next 25 years. Is this likely? What would be the economic fall out? Do we have any choice if the oil dries up?

The good news is that the world energy consumption growth is slower than the world economy. Not so much for just theUS. Will it continue/increase this trend as oil runs out?

A historical view of energy consumption trends.

And look who's producing the emissions. But also look at where the people are - what if China, Indea, Asia increase their energy consumption? And why should they when the US is producing such a lion's share? Not unrelated to the plot below....

Anyone want to put bets on when the Ford Explorer will be a dead as the dodo?