Friday, 22 November 2013

Reducing the Global Temperature in One Swell Foop

When various news items share a brain for a while, they are likely to connect. My brain holds, for example, that the existence of global warming is a consensus among scientists, but that they like to call it "climate change" these days. Those facts share brain space with knowledge that carbon dioxide is a greenhouse gas, contributing to global warming, that greenery takes up carbon from the air and sequesters it, reducing the amount of carbon dioxide in the air, that parts of the Gobi Desert are being reclaimed for greenery and that the Sahara Desert is expanding. I know that sea water can be desalinated, if there is sufficient energy for the job, and that a big enough supply of fresh water can cool and irrigate the fringes of a desert, driving them back. These points, connected, raise the innocent question of whether a large part of the campaign to limit global warming should be devoted to making the Sahara green. Let us investigate whether what I "know" is valid before I make up my mind.

The reality of global warming

Al Gore, a former Vice President and almost, at one time, the President of the United States, is quite convinced that the rise of atmospheric carbon dioxide, which was due to human activity, was leading to hotter climates. In 2006, he expressed his opinions in an Oscar-winning documentary with a wonderful title, An Inconvenient Truth. The film may have helped him to win a Nobel Peace Prize the next year. It did win him a storm of controversy that can be glimpsed on Youtube as well as in print.

On the other hand, his views are widely shared, despite their inconvenience. One study of climate change studies found a 97% consensus that human activities are causing the average temperature of the world to rise. (The inevitable criticism of the study is here.  Shame on you Forbes! The reply to the criticism is here).

Even NASA takes a stand that humans contribute to global warming. It says
Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities, and most of the leading scientific organizations worldwide have issued public statements endorsing this position. The following is a partial list of these organizations, along with links to their published statements and a selection of related resources.
Other respected organizations have released statements along the same line line, including the American Association for the Advancement of Science (AAAS), the American Chemical Society, the American Geophysical Union, the American Meteorological Society, and the U.S. National Academy of Sciences. In other words, there is no controversy among the best informed scientists that global warming is real and that humans are contributing to it.

The growth (or not) of the Sahara Desert

The Sahara Desert, according to the appropriate Wikipedia article, covers over 9,400,000 square kilometres (3,600,000 sq mi). It is about the same size as the United States now, but it has been growing at the rate of 30 mi per year. That rate may slow and even reverse as a paradoxical by-product of climate change. However, there are more deserts than the Sahara, so a hotter world will be a drier world, on the whole, and one with more desert.

We Have the Technology (and Some Experience)

The expansion of the deserts could be slowed, and even reversed, by human efforts if enough clean water were available to create a self-sustaining ecology. We have the technology to provide the water and to introduce such ecologies. For example, the Desert Rose concept uses solar energy for desalination, then introduces nitrogen-fixing plants to stabilize the soil. The Seawater Greenhouse distills seawater in, as it says on the tin, greenhouses, but is otherwise similar. Other methods of reclamation focus on stabilizing the soil rather than providing the water.

An interesting and successful experiment in creating a self-sustaining ecology on a burnt-out cinder of land took place on Ascension Island, in the Pacific, thanks to an idea from Charles Darwin and the help of Joseph Hooker and the Royal Navy. I quote from a BBC News article on the experiment.
Ascension was an arid island, buffeted by dry trade winds from southern Africa. Devoid of trees at the time of Darwin and Hooker's visits, the little rain that did fall quickly evaporated away.
Egged on by Darwin, in 1847 Hooker advised the Royal Navy to set in motion an elaborate plan. With the help of Kew Gardens - where Hooker's father was director - shipments of trees were to be sent to Ascension.
The idea was breathtakingly simple. Trees would capture more rain, reduce evaporation and create rich, loamy soils. The "cinder" would become a garden.
So, beginning in 1850 and continuing year after year, ships started to come. Each deposited a motley assortment of plants from botanical gardens in Europe, South Africa and Argentina.
Soon, on the highest peak at 859m (2,817ft), great changes were afoot. By the late 1870s, eucalyptus, Norfolk Island pine, bamboo, and banana had all run riot.

The Cooling Effects of a Green Sahara

A desert turned green would curb global warming in three ways:
  1. by absorbing a major greenhouse gas, carbon dioxide, and storing much of its carbon in tree trunks and soil; 
  2. by absorbing sunlight in the trees' leaves before it can warm the earth; 
  3. and by creating a region of evaporated water, which not only cools the local area but creates clouds, which then travel, cooling more distant areas by reflecting light, creating shadow, and depositing rain.
So much is the theory, but would transformed deserts have enough of an effect to counteract man's contribution to global warming?

How Much of an Effect?

The effect of desert greening depends on how much desert you green and how much cooling effect the greenery produces. Let us start with the question, "How much desert could, potentially, be greened?"

Deserts, defined as areas with "a moisture deficit" make up a substantial portion of the world--33% of the world's land--but that includes Antarctica. However, just three of the biggest hot deserts constitute a large area by any standard. The Sahara has about 9,400,000 square kilometres; the Arabian, 2,333,000; and the Gobi, 1,300,000. I am leaving out the Australian desert because, in the words of Randy Newman, "I don't want to hurt no kangaroo." The Sahara, Arabian, and Gobi deserts together give us 13,033,000 square kilometres.

If I could find a figure for the cooling effect of a single square kilometre of such a forest, we could start to have a very interesting discussion about the economics of greening the deserts. Unfortunately, that information is not available or is not easily found through an internet search. However, an article on biosequestration mentions that "The Intergovernmental Panel on Climate Change (IPCC) estimates that the cutting down of forests is now contributing close to 20 per cent of the overall greenhouse gases entering the atmosphere." If reversing the deforestation could cut 20% from the greenhouse gasses, the creation of large new forests would do even more.

Not an Original Idea

This is not a new idea, of course. Two worthy projects are operating now: the  The Great Green Wall and Sahara Forest Project. However, the first is only trying to hold the line so that the Sahara will not expand further and the second is just beginning. The fully operational Sahara Forest Project Pilot Plant was opened in Qatar only in December 2012. China's Three-North Shelter Forest Program is also focused on limiting the Gobi Desert's spread. Despite having created the world's largest artificial forest, this project would have to operate for three hundred years to reclaim the desertified land.

Problems, Political, Economic, and Cultural

There are problems with the idea of taking responsibility for tweaking the Earth's climate. First and foremost is the idea of taking responsibility. There was a time when cities dumped raw sewage into the sea, not knowing or caring where it would travel. "Nature would take care of it." Ask the people who live downcurrent of Victoria, BC about that and they will tell you that nature isn't doing the job. Billion-dollar sewage treatment plants are a painful alternative to blissful ignorance.

Taking responsibility for the climate would be an even longer-term, more international, and more expensive responsibility. The countries covered with desert could not pay for the project that turns bare sand and stone into soil and trees. The money would have to come from more fortunate countries, a difficult trick to manage.

The local problem, putting aside the political instability and corruption of many states near the great deserts, is that people whose cultures grew up in desert would have to change their ways. The Bedouin, for example, know how to live in desert. Though their numbers are not great, their antagonism could make the project impossible. Would they be willing to adapt to a new environment?

I think they might. The desert landscape may be appreciated best by those who live somewhere else. I recall Alec Guinness, playing an Arab leader, lecturing an Englishman in the film Lawrence of Arabia, making this point: "I think you are another of these desert-loving English...," he said, and listed a few of them; "No Arab loves the desert. We love water and green trees, there is nothing in the desert. No man needs nothing."

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