It’s been a pleasant autumn at Cottarton with long stretches of dry warm days. The farmers are happy, because they were able to harvest their barley ahead of schedule. Our vegetables this year were stellar: gigantic zucchini, tomatoes, carrots, parsnip. Amber greets them in the kitchen with a mixture of elation and dread. More pickling to do? This year’s success story is our chrysanthemums --- still going strong, decorating every room in our cottage. We give many bunches to our friends.
These days I’m engaged in the long job of forking over the vegetable beds. Our neighbour, Hugh, is delivering a load of dung that will be spread out over winter so that it properly rots in, to be ready for next spring’s planting.
Meanwhile I’ve taken out a library card at Aberdeen University to study the Earth’s climate. Not the global warming thing. I want to know how the climate changed over the past 100 million years, and why. The story reads like a whodunit. As a geologist I’ve studied for twenty years the oceans rise and fall, because these result in deposition of sandstones and shales that we drill for to find some reserves. Its no secret that every 20-100 thousand years during the past 10 million years the oceans go through a cycle of rising and falling. The Earth gets warmer and cools, mostly a result of changes in the earth’s tilt. But several extraordinary anomalies are evident. During the Eocene, 50 million years ago the Earth was 6 degrees warmer than it is today --- but the sun was somewhat cooler. What gives?
Before I offer an explanation I’ll say that I am not a climate expert. The internet is full of those who make that claim. If you check out the blogosphere you’ll find that everyone who has taken a science course is out there pontificating about climate change, claiming to be a expert. In their recent book, “Superfreakanomics”, Steven D Levitt and Stephen J Dubner, two economists, argue that global warming is nonsense. Even if it’s true, then why not spray some stuff into the air to counteract global warming? A much cheaper solution than for us give up driving our SUVs. I have a Master’s in Astronomy and one in Geophysics, two disciplines that are necessary if one is to understand climate change. Yet I feel totally inadequate to enter into a scientific debate on the subject. Remarkable that those economists who have less background in the field, don’t have such srcupules. Their book will no doubt be a best seller. There’s also the science fiction writer Michael Crichton who wrote “State of Fear” a SF novel that suggests that the global warming movement is a global conspiracy. The guy was called to Capital Hill to testify in front of the US Senate as a “climate expert.” I can think of many people they might have chosen, but then those --- real experts, might not have given the Senate committee the answers they wanted to hear.
So why was the Earth so warm in the Eocene? One source I consulted suggests that it was caused by a sudden emission of methane. Then, as today, there are large amounts of methane stored under the ocean floor in the form of gas hydrates. A small warming could release the methane into the atmosphere. Once there, methane, even more than carbon dioxide makes our atmosphere more impervious to heat, so that our earth behaves like a greenhouse. All this makes me think of what might happen to the gas hydrates that I saw in seismic data while I worked for ExxonMobil, should a small increase in our present temperature result in an analogous warming. It would be scary. I’m no climate scientist, so I’ll defer to those who are in that line of work.
Meanwhile, I’m reading about the recent ice ages. I’d like to know why the last one came to an end about 14,000 years ago, to give us our present, very pleasant climate.
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