Daniel Schrag: Climate Science & Climate Change
Notes from a lecture given as part of:
IGA-310 Energy Policy: Technologies, Systems & Markets
22nd September 2010
Prof Daniel Schrag
Atmospheric C02 hasn’t been above 300 parts per million in last 600,000 years, with large fluctuations, until recently. Likely to rise to over 600. Currently c390.
Just because there are natural cycles doesn’t mean that human actions aren’t significant.
Equator is place of stability, so melting there is v significant.
Key question is whether rate of change can be accommodated. Previous historic change
We know C02 is a greenhouse gas, we see it going up and we know it’s happening faster than ever before in history.
Can we prove that C02 is causing the warming? We can’t but you’d be a fool to bet against it.
C34 million years ago, ice formed at poles, leading to greater seasonal variation, with ice reflecting heat.
Likely to be worse than scientists forecasts since scientists work to 95% confidence intervals cf military <50%.
People don't experience global avg temp, they experience local effects.
Guarantee there will be surprises.
Gulf Stream is NOT caused by ocean currents but by winds created by circulation of the earth, which is not going to stop spinning.l
Boston has cold winters because of westerly winds not because of Gulf Stream.
London benefits from ocean, which absorbs heat in summer and release in winter.
So, Cape Cod 10 degrees warmer in winter than Boston but cooler in summer.
Pacific Ocean thermocline, warmer in west and cooler in east, w cold water closer to surface. El Nino brings warmer water to east, with global effects.
North West Passage opened from ice in 2007 cf Panama Canal. Plus thick ice at 50% of 2007 levels.
North east passage has opened too.
Key about sea ice is reflection of sun and insulation of sea from atmosphere.
Rain on ice sheets is problematic.
250 cubic kilometres of ice being lost from Greenland per year = 5mm per year.
But unclear if rate of melt is steady.
Ross Ice Shelf – high consequence, low probability event? We don't actually know. Its a known unknown. Lots of sea level bound up in ice sheets.
Building a sea wall is not a long-term strategy.
500 billion tonnes of C02 in permafrost which, if released (from microbe action) into atmosphere is greater than all fossil fuel burned to date.
Problem is going to be with us for a long time.
Eg if all fossil fuel burned, atmospheric carbon likely to peak below 2,000 parts per million, then settle c 400 for tens of thousands of years.
What can be done?
European negotiators obsess on timescales
But what matters are cumulative emissions over a time period of c100 years
Most likely way forward is to grow emissions to build up capacity then reduce rapidly.
Prob of cap and trade on linear path is that best path may not follow.
Impact = population x affluence x technology
Emissions = pop x GDP/person x emissions/GDP
Isn't problem about population growth
Not entirely true. Growth from 6 to 9 billion growth is only 50%.
Economists predict global GDP will grow from 20 trillion 2008 to 250-500 trillion by 2100.
Problem is therefore because people are richer and therefore more carbon emitting.
US and China accountable for 50% of emissions.
Africa doesn't figure in emissions reductions.
One of problems of Kyoto is involvement of everyone.
Better for smaller group eg bilateral US/China.
What Obama did was v imp because he got China, Brazil, South Frica into room to set new direction.
British and German cuts were achievable because Britain had ended coal industry and Germany anticipating reunification and removal of inefficient East German practice.
Ways to reduce emissions of C02
1. Use less energy – efficiency/conservation
2. Non- fossil fuel energy: renewables and nuclear
3. Carbon capture and storage
Nees to be thought of as a threat similar to terrorism.
Some detractive interference between factors eg oust on 1. Will drive price of energy down.
Price matters (linear correlation of efficiency of use versus price of energy)
Ccalifornia uses 40% less energy per capital than rest of US, effect of Gov Brown in 1970s
Electricity generation by state
This an experiment on planet not performed for millions of years
Poss more than predicted
Stabilizing greenhouse levels is possible but looks unlikely now
So massive suffering by human societies and natural ecosystems is likely
Churchill – democracy is the worst form of government apart from the alternative
[Longer applause than the polite norm]