Photosynthesis enables trees to take carbon dioxide in through their leaves and swap it for oxygen. They use the sequestered carbon to make molecules like cellulose and thus more trees. So rich people who love to burn things containing carbon…like petrol and aircraft fuel…pay others to plant trees on their behalf on the assumption that planting trees cools the world down. Nice idea but probably wrong.
Trees being generally green and bristly remain quite a dark shade even after a blizzard. They are certainly darker than grasslands smothered in snow. Thus they can absorb more of the sun’s heat than vegetation which might otherwise cover the same stretch of land.
Then there is transpiration…the process by which plants suck up groundwater and evaporate it into the atmosphere. Woodlands are usually better than other ecosystems at getting water vapour into the air. In warm places this tends to make things cloudier and those clouds in turn reflect the sun’s heat back into space.
Dr Govindasamy Bala at the Lawrence Livermore National Laboratory in California has built a computer model to reflect these realities. Unlike most climate-change models…with their list of greenhouse gas absorbing and radiating heat…Dr Bala’s Integrated Climate and Carbon Model (ICC) has sub-sections that represent how the carbon cycle actually works…and how it influences climate. Thus Dr Bala’s model can be told to replace all the world’s forests with shrubby grasslands and work out how such a change would influence the temperature in different places on the planet.
Perhaps one day HAL or Deep Thought…or some other clever offspring of the ICC computer model…might have a sector for people. People produce five times as much carbon dioxide as industry…they breath in oxygen and breathe out carbon dioxide…so an alternative strategy for rich people who like flying off to far-flung places would be to slaughter three-quarters of the world’s population…although then they would have no one to drive their aeroplanes. But back to Dr Bula’s forests.
When Dr Bala ordered global clear-cutting, his model calculated that the carbon dioxide levels would double by 2100…and produce not global warming but nuclear winter. Here is why. Brighter high latitudes reflect more sunlight in winter cooling the environment but because the tropics are less cloudy they warm up. Dr Bala’s computer predicts that a treeless world would be a degree or so cooler. His findings were published recently in the Proceedings of the National Academy of Sciences.
Of course the more sceptical among us have to wonder if Dr Bula made any allowance for all the sheep that would find their way onto the new grasslands after their subsequent enclosure by the rich and powerful. England has as many sheep as people. Sheep give out greenhouse gases from both ends of their anatomy…carbon dioxide from one end and methane from the other. Then there are cows and horses, dogs and cats. Cows are responsible for a third of Ireland’s greenhouse gas emissions. And England is famous for having more cats than people. But let us stay with its forests and woodlands. Should it be public policy to hound the Carbon Offsetters out of business? Regrettably the real world is not so simple.
According to the Livermore Model cutting down trees in Russia and Canada leads to local cooling but the released carbon dioxide spreads itself about and warms the whole world. But around the equator warming acts locally as well as globally so tropical countries warms themselves up when they let in the loggers. Offsetting is double or quits for the Amazon rain forest…but hypocrisy in Europe and North America.
On the other hand computers are nothing more than great big dumb calculating machines where garbage in guarantees garbage out. The more expensive the computer, the faster the doctored data gets pumped in and the sooner half-baked nonsense pours out. Scientists are beginning to lack all credibility. It is already necessary for research findings to carry government health warnings that might go something like this.
‘Predictions based on computer modelling. Half of all scientific predictions may be wrong but unfortunately nobody has the foggiest idea which half. For budgeting purposes please assume that temperatures can go down as well as up but unfortunately nobody has a clue when and where and by how much. Design criteria should be based on fuzziness and redundancy. Effective rapid response capabilities should be in place to deal with problems as and when and where they arise. When in doubt don’t just do something stand there.’
In other words quit meddling with the planet and stop trying to control its climate.