June 2009 Archives
Superposition means putting one thing on top of another. Nature does it all the time, but it is only in the past thousand years or so that we have worked out how to exploit it. Ibn Sina, an 11th-century Persian better known in the West as Avicenna, understood how Nature piles younger sediment on top of older, and Leonardo came very close. The first person to articulate the Principle of Superposition clearly, though, was a 17th-century Dane, Steno: In any pile of sediment, the youngest is on top and the oldest is on the bottom.
It is an idea so blindingly obvious as to sound stupid, but for a long time the obviousness blinded us to its potential: depth in the pile is equivalent to time before the date of the top. With patience and hard work, there is a historical record waiting there for us to decode.
There are exceptions that prove the rule. For example folding can overturn the layers. Little beasts that live just under the sea floor can blur the layers by burrowing. In glaciers, where the accumulating snow is a sediment just as much as the mud on the sea floor, the main problems are flow, which stretches and squeezes the layers, and refreezing of meltwater, which mixes this year's accumulation with that of earlier years. A satisfactory solution is to drill at the summit of an ice sheet, where there is no melting and the flow rate is negligible.
The payoff has been invaluable. Ice cores give us our most detailed picture of the Earth's history over the past million years. We have barely begun to unravel the story. The wealth of incident in the story is so rich that it is hard to know how to pick and choose, but a recent technical advance by Elizabeth Thomas and colleagues makes a good start. They cut slices just 2 millimetres thick from a 4.5-metre section of a core from the interior of the Greenland Ice Sheet. This section, 2070 metres beneath the surface, is estimated to represent the years from 36,401 to 36,169 BC - at a rate of 7 to 11 samples per year. The assignment of calendar years is a bit dodgy. The dates could be out by more than 1400 years. But the relative error, from bottom to top of the section, is only about three years, and the march of the seasons all those years ago can be seen distinctly in the varying concentrations of dissolved ions. We also learn interesting facts such as that 36,263 BC was a rather dry year, while 36,262 BC was so-so and 36,261 BC rather snowy.
There is more to this work than minute detail. It tells the story of the transition from a full glacial state to the warm climatic stage DO-8. The last ice age is peppered with these DO or Dansgaard-Oeschger events, warmer episodes that lasted 1000-1500 years and began abruptly.
The authors are properly cautious about interpretation. Their aim was more to show what attention to detail can uncover than to write the last word about the transition to DO-8. But they do suggest that the transition lasted just 21 years, during which snowfall increased by a half and temperature rose by 11.4 °C. This last number calls for particular caution. It needs to be seen in context, because it probably represents a local rather than a global change, and there are some technical complications to be sorted out. But at face value it implies warming at 0.5°C per year, a hundred times faster than the global warming of the 20th century and ten times faster than some extreme predictions for the 21st century.
Dansgaard-Oeschger transitions are not like the warming that is about to happen this century. For one thing, they are almost certainly not due to increases in greenhouse-gas concentrations, at least not primarily. They are more probably related to abrupt changes in the circulation of the north Atlantic Ocean. But they do share the attribute of abruptness with our near future, and that makes them intensely interesting. Avicenna and Leonardo would have understood why.
With the climate conference in Copenhagen in December seen by many as the make-or-break event, the EU position is relatively clear- a 20% by 2020 cut in emissions (from 1990 levels), unless a good global agreement can be reached, when the target would be raised to 30%.
The UK is amongst the leaders in pushing for high targets. The Budget in April set what was claimed as the world's first carbon budget, as required by the new Climate Change Act, with a legally binding 34% reduction in emissions by 2020. The government said it will 'increase the level of ambition of carbon budgets once a satisfactory global deal on climate change is reached'. Longer term, there is a firm commitment to an 80% cut by 2050.
While welcome, all that will mean very little if the US and China don't come up with decent targets. The good news from the USA is that, after years of denial under Bush, the US government now sees greenhouse emissions as a major issue: the Environmental Protection Agency is now regulating them. And progress is being made on national targets. Against strong opposition, the House of Representatives has just voted 219 to 212 to bind the US to cutting carbon emissions by 17% from 2005 levels by 2020 and by 83% by 2050. It also agreed that a national carbon 'cap and trade' system should be established and to a 15% 2020 target for electricity from renewables. However this has still all to be passed by Senate- where opposition is likely to be even stronger.
The opposition has already led to watering down of targets. For example, the draft US Clean Energy act called for a 20% cut on 2005 emission levels by 2020, and for the US to get 25% of its electricity from renewables by 2025. The fossil lobby wanted just a 6% cut by 2020 and lower renewable targets. Even so, the emission level now agreed by the House of Representatives (17%) is a significant compromise and the 15% target for electricity from renewables is an even bigger compromise, especially since it seems 12% could be allowed in some regions with poor resources, and energy efficiency gains may be allowed as a substitute for some renewables.
In any case, even if finally passed into law through Senate, these are just paper targets. The crucial thing is the proposed new US Carbon trading system - a key element in translating the targets into reality. Indeed, although much was made of the £150 billion over ten years that Obama allocated to renewables and other green energy projects earlier this year, as part of the US Economic stimulus package, much of that funding will only materialise if the carbon trading system goes ahead. This may explain why the very large stimulus allocation (around 10 times current support levels) was not fought much by Republicans- they may have been waiting to block it at source by opposing the Carbon trading system. If that is proves to be the case, the fear is that the new proposals won't get through in time for the USA to make a clearly positive contribution at the Copenhagen conference.
While this may be a problem, it seems that the simple fact that Obama is now taking the US into climate negotiations has been enough for the Chinese to engage in the process more fruitfully - and that in turn has helped Obama, since one of the main reasons for opposition to the Kyoto protocol in the US was that it didn't apply to newly developing countries like China, whose emissions were expanding rapidly. They have actually recently overtaken the US. But China now seems to be thinking in terms of, if not absolute cuts, then at least a commitment to the reductions in the growth of its rapidly expanding carbon emissions.
Su Wei, a leading figure in China's climate change negotiating team, said that officials were considering introducing a national target that would limit emissions relative to economic growth in the country's next 5-year plan from 2011.'China hasn't reached the stage where we can reduce overall emissions, but we can reduce energy intensity and carbon intensity.' i.e. carbon emissions/GNP. Whether an agreement will be reached on that before the Copenhagen conference remains to be seen.
The stakes are high- for Obama and for the world. The EU is pushing hard, and, whatever might be happening at home, the USA seems to be bending over backwards to get a global agreement. It has proposed that developing nations like China should not be required to commit to specific emission targets, but should be asked to commit to boosting energy efficiency standards and improving the take-up of renewable energy. And there are positive signs, with talk of China being able to go beyond the current target of getting 15% of all energy from renewables by 2020, to 18% and possibly 20% - on a par with the EU and well ahead of the USA.
We may make it yet.
Waxman-Markey, a bill "to create clean energy jobs, achieve energy independence, reduce global warming pollution and transition to a clean energy economy" is voted on by end of this week in the House." A lot of attention has highlighted the global warming parts of the bill, and rightly so. In the current draft, the emission reduction target is 17% reduction from 2005 levels by 2020. This is not more than 4% reduction by 1990 level and may be not enough to persuade China, Europe and other world regions to get tougher on their own targets. Also, potentially ineffective offsets can be purchased, hence avoiding emission reduction at the smokestack.
However, the bill is surprisingly comprehensive in addressing also large-scale clean energy deployment, sustainable transportation, smart grid advances and transmission issues. All these measures support a transition to a clean energy economy, as the bill claims.
In particular, Waxman-Markey holds quite some promise, as it
- aims to invest $190 billion into renewable energies
- provides grants for transmission infrastructure and requires coordination of electricity transmission planning with the goal of building out the grid to facilitate deployment of renewables (i.e., brings the wind energy of the Mid-West to urban centers)
- asks regional electric grid planning to take into account all significant demand-side and supply-side options, including energy efficiency, distributed generation, renewable energy and zero-carbon electricity generation technologies, smart-grid technologies and practices, demand response, electricity storage, voltage regulation technologies, and even more detailed measures. (Thanks to Cathy Kunckel for pointing this out.)
And this transition is actually the bottom line. Make it more lucrative to invest in renewable energies than in coal plans, more attractive to move into mixed-use neighborhoods with high-quality public transit than relying on gas-guzzling monsters in ex-urbia. If the bill heads into this directions, it will be a huge success for avoiding disastrous human-made climate change. Currently, utilities have expertise in operating coal plants and know this market. However, when coal plants get a little bit more expensive to operate and renewable energies get a little cheaper to deploy, utilities start to reconsider their investment decisions. And one point the market may switch over to new technologies, like wind, geothermal and concentrated solar power. The current gradual change can accelerate to a switch in the way our energy economy operates. If that happens, weak targets in emission reductions can much more easily be strengthened; the system dynamics have changed and there is less strong interest anymore in coal plants.
One of the emergent technologies is wind. It is mature by now, the market is well developed, and in many locations in the US, wind is cost competitive to conventional sources of energy. With more policy attention on the grid infrastructure, a wave of investment into wind energy within the next years can be expected. For example, a study published in PNAS points out that US wind resources, particularly in the central plain states, could supply 16 times more energy than the current total US demand.
