John Harte from UC, Berkeley spoke to Berkeley Friends (Quakers) Thursday night. I’ve altered what he said very slightly.
For the first time people can alter the Earth at a global scale, rather than just polluting locally. In the 1960s, when Harte began work, there was still discussion as to whether the cooling effect of particulates being added to the atmosphere via coal, oil, and wood or the warming due to the greenhouse gases would dominate, but by the early 1970s, it was clear to pretty much everyone that greenhouse gases would dominate. By the mid-20th century, we should see warming on the same scale as from the depth of the ice age to now.
Scientists don’t prove anything, not gravity, not evolution, not climate change. What they do is amass more and more evidence until alternative explanations are disproved. The following is not proven, but there is enormous evidence: lots of validating data, and no contradicting data.
The atmosphere is mostly nitrogen and oxygen gas, 2 atom molecules. The greenhouse gases, such as CO2, H2O, N2O (nitrous oxide), CH4 (methane), the CFCs, and O3 (ozone) are 3 or more atoms. They absorb the heat (infrared light) leaving Earth, and re-radiate it. Some of this reaches the Earth again, sometimes many times, rather than just escaping into space. This is the greenhouse effect.
The concept dates back to Arrhenius, a Nobel-winning chemist who used a slide rule to figure out that if the amount of atmospheric greenhouse gases doubled, there would be an increase in surface temperature of 3 C. Carbon has gone about 30% since then, and methane 70%. So the temperature should have gone up about 0.6 C, as it has. By 2050, on our current trajectory, the temperature increase should be 1.5 – 2 C, even up to 4.5 C. At the end of the last ice age 20,000 years ago, at the coldest, the temperature was 8 – 9 C less than today, so the projected increase by mid-century, say 3 C, is almost half as large. The world was a very different place 8 – 9 C ago.
Current estimates of temperature increases could be underestimates. Most of the feedbacks not considered in the models are positive feedbacks. For example, warmed soil or peat bogs release carbon and methane because of the increase in bacterial activity. Soils contain much more carbon than does the atmosphere. Or in the same way that warmed beer goes flat, imagine the ocean as an enormous glass of beer. Warmed oceans may release carbon, or absorb less carbon – and oceans contain 50 times as much carbon as does the atmosphere. There are possible negative feedbacks as well, such as trees responding to increased carbon by growing faster and bigger. But the best estimates are that the negative feedbacks are small effects, and much smaller than the positive feedbacks.
As the Earth warmed out of the last ice age, from 20,000 years ago until 500 year ago, atmospheric carbon increased. What caused this? We don’t know and it’s not in the models. John Harte expanded on this when someone asked a question about Fred Singer’s position that carbon appears to increase 300 years after warming, and not the other way around. First, increased carbon follows warming and then is followed by increased warming. There is not enough precision in the data to say that it follows by 300 years. The push into and out of the ice ages is caused by orbital changes. As the Earth warms, there are changes on the Earth, eg more plants and a warmer ocean, etc, some of which would reduce carbon and some increase carbon and the net result of warming is more carbon, a positive feedback. It is very worrisome that we don’t really understand the various mechanisms.
Why accept the current model? It makes a prediction that temperature will go up, but that’s only one prediction. However, there is a fingerprint – the details of what that warming look like, that match very well what the model predicts. For example, the model predicts correctly more warming at night (hotter sun would predict the opposite), warming of the atmosphere but cooling of the upper atmosphere (because the heat isn’t making it out, again, the opposite effect from what one would predict if the increase came from increased solar radiation), more warming in polar regions than in the temperate and tropical regions.
Some people must be predicting that we’re about to go into an ice age so it’s good to have solar warming, because more than once professor Harte said leave the fossil fuels unused for when we do go back into an ice age in 3,000 years.
The average surface temperature is now warmer than it’s been in at least 750,000 years and possibly warmer than any time since the dinosaurs 65 million years ago, since the age of mammals began.
Some time was spent on addressing the various challenges put up by people who disagreed, such as the discrepancy in warming observed by satellites (it was an equipment calibration problem). The biggest myth is that we can’t afford to address climate change.
The possible impacts are why climate change is such a concern. For Harte, the biggest single issue will be the complications for food production, though others might choose other problems as the most important complication. The interiors of large continental areas are often the breadbasket; this is even more true in central Europe than in the US. Both will likely dry up, and the frequency of serious droughts will increase. Even if there is more rain, increased temperatures mean dryer soil. The sources for irrigation will also dry up. Are we going to desalinate water on the coasts and ship in?
So agriculture could be seriously impaired. Rising sea levels would endanger South Pacific Island nations. Cities would experience more frequent and intense heat waves. Arizona last year had temperatures above 115 – 118 F for several days, an urban heat island effect exacerbated by climate change. There could be more frequent and intense wild fires. In California a 4 – 5 year drought ended last winter, but while snow pack and spring runoff were down, we had 5 years of bad fires.
The hurricanes this fall were fueled by sea-surface temperature, which is expected to increase. On the other hand, it’s an open question as to whether tropical diseases will spread as temperate regions become warmer and dryer. There will be ecological effects. Tropical coral reefs are now at 75 – 78 F; they could bleach — die — if ocean temperatures rise above 80 F, as they are likely to do. Coral reefs are a huge source of protein for local peoples (fish live in and breed in the reefs). The reefs protect atolls from storm surges.
What can we do?
• Exercise consumer choices: walk to work, recycle, solar panels, Everyday choices can decrease energy use.
• Government action – the most important of which is to follow in the steps of Nixon, Ford, and Reagan who supported increasing fuel efficiency. We could increase it to 35 mpg today, including SUV’s. [Editorial note: that may require a mix including more smaller cars.] Improving fuel efficiency is the most important of the solutions for the US. Also, increase appliance and light bulb efficiency.
Fund R&D into clean renewables such as wind and photovoltaic. We shouldn’t totally write off nuclear power and should continue to fund research.
Promote higher efficiency and lower carbon solutions.
• Protect old growth forest here and elsewhere. They add carbon to the atmosphere when they are cut down (the second largest source after burning fossil fuels), decrease biodiversity, affect the local climate, and so on. [Editorial note: trees and all living organisms contain carbon. The fossil fuels are dead organisms, morphed into natural gas or coal or petroleum. Cutting down large old trees and replacing them with new trees means that there is a substantial net increase in carbon released from burning or rotting tree. Even if the tree is used for your house, and very little of it rots or burns, the new ecosystem that comes up will not be capable of supporting the range of species that old growth forests can.] In answer to a question, Harte said that storing carbon in trees and then using them for houses may not be bad, it requires looking at the analysis (but not old growth!)
• Put in place mechanisms for wise consumer choices, such as photovoltaics and better windows. This is usually presented in the form of a carbon tax, though Harte wonders if there are other solutions that will hurt the poor less. His particular suggestion was tax breaks or credits for the better choices, which he thought might achieve the same goals with less pain for the poor.
In response to a question on the effect of changes in the Gulf Stream, it appears that a couple of years ago people figured out that Europe is warmer than the eastern US not because of the Gulf Stream but because of the Rockies. The Gulf Stream warms Europe by about a degree C, but the Rockies force the westerlies up into Canada, and by the time they come south again, all is a wee bit cooler. So the Gulf Stream may not have a large effect on cooling Europe. [Editorial note: but may have effects on rains and monsoons and droughts worldwide. Unless that’s changed as well!]
Someone asked about what we’ve seen from climate change locally. We’ve seen droughts, but are they due to global warming? All that can be said is that this is part of the predictions made by models: we expect to see more droughts, and more intense droughts. We expect to see hotter years, and the hottest years in our history have been in the last decade [editorial note: includes 2001 – 2005 but not in that order, plus 1998, an El Nino year]. So hot years, droughts, forest fires, we can say these are probably caused by global warming, but we can’t say for sure.
We were left with much to consider, both the implications of climate change and actions we might consider. I know that both Berkeley Meetings plan to consider these topics again.
