Читать книгу Harmony: A New Way of Looking at Our World - Tony Juniper - Страница 11

What I have been told by scientists for years has finally been accepted as common knowledge – at least among those prepared to face the facts. From humanitarian disasters on a grand scale to extreme conditions causing massive costs to the insurance industry, and from the inundation of low-lying coastal areas to the disappearance of rainforests owing to prolonged droughts, we could soon witness profound challenges that could become unmanageable if we do not act in time. The consequences for hundreds of millions of people living in developing countries will be disproportionately worse – although, for many, they already are. Having said this, it is not only the poorer nations that will suffer the short-term shocks caused by extremes in the weather. The devastation wrought on New Orleans by Hurricane Katrina is a recent case in point. I saw with my own eyes the impact of that catastrophe – and it is sobering to remember that it occurred in the world’s richest economy.

In addition to more extreme conditions, including severe floods, droughts and heatwaves, there is good reason to be seriously concerned about what in the jargon is known as ‘non-linear’ change. This basically means change that is not smooth and gradual, but sudden and dramatic. One example that is taking place right now before our very eyes is the rapid loss of the Arctic ice sheet. I recently heard from the polar explorer, Pen Hadow, how fast this is happening – much faster than scientists predicted even a few years ago.

My wife and I visited New Orleans about two months after Hurricane Katrina hit the city. We were appalled to see the extent of the damage caused there. This event demonstrates how we are all at risk, rich and poor alike.

This image shows the extent of sea ice in the Arctic at the end of the melt season in September 2008. In recent years there have been record levels of open ocean as the ice has melted to new low points. This rapid large-scale change threatens both wildlife and the traditional livelihoods of indigenous people.

In the late Summer of 2007 an area of the Arctic sea ice twice the size of Great Britain disappeared over a couple of weeks – an event never before witnessed. The same thing happened in 2008. On the basis of recent events, and rates of warming in the Arctic region which are far higher than the global average, some believe that in twenty to thirty years the Arctic Ocean could be virtually free of sea ice in Summer. Some projections suggest that this will happen even sooner. There are also signs of rapid change in Antarctica. The British Antarctic Survey recently explained to me that, out of 244 glaciers on the Antarctic Peninsula that have been monitored for the past fifty years, some 87 per cent of them have been in retreat. The Greenland ice cap is also showing signs of increasingly rapid melting – and should the whole lot melt it will eventually add something like seven metres to the average global sea level.

The loss of ice is also serious because ice acts like a mirror reflecting the Sun’s energy back into space. When it is gone, it is replaced by darker ocean and land beneath, which absorb some 90 per cent of the energy coming in, whereas the ice would have reflected 80 per cent of this back again. This effect is known as a positive feedback, whereby the warming leads to changes that cause more warming, no matter what we do. And unfortunately this is not the only effect. The warmer our atmosphere gets, the more numerous and dangerous the different ‘feedbacks’ are expected to become. These range from the melting of permafrost, which leads to the release of billions of tonnes of carbon dioxide and methane (a very potent greenhouse gas) to the billions of tonnes of green-house gases that would also be released as rainforests die back. These are, to leading climate scientists around the world, signs of global imbalance.

A weathered barn collapsed in Alaska, USA, due to permafrost melt and unstable foundation conditions. Once the frozen ground provided a solid base to buildings, roads and pipelines, but the thawing of permafrost is causing widespread damage to these structures.

As far as climate change is concerned, there is now a strong consensus that, in order to avoid the worst consequences of what we have put in train, it will be necessary for us to limit global average temperature increase to no more than two degrees Celsius above the average temperature prevailing at the end of the pre-industrial period – that is, in the late eighteenth century. A two-degree change between then and the near future may not seem very much, but as a shift in the global average it is a vast change, and in some areas it will be a lot bigger – in the Arctic, for example.

Temperatures even three degrees above the pre-industrial average have not been seen since the Pliocene period, some three million years ago. At that time sea levels were up to 25 metres higher than now. The last time our planet saw a comparable four degrees of warming was millions of years before then, and five degrees perhaps some 55 million years ago, at the beginning of the Eocene. At that time the Earth was virtually ice-free, with the average sea level some 75 metres higher than now. Animals such as marine turtles that today we associate with the tropics and sub-tropics lived at polar latitudes. A world that is on average four degrees warmer than now would be very different, and would undoubtedly bring very major upheavals and create major risks for most of humanity.

I recently visited the Met Office Hadley Centre for climate research at Exeter, in Devon, England, where scientists confirmed to me that a four-degree temperature increase during the second half of this century is to be expected on the basis of ‘business as usual’ emissions, should we not act now. However, it could be higher than this with the worst-case scenario for the end of the twenty-first century, suggesting it is conceivable by then that average global temperatures will rise by over six degrees. To put that into perspective, a rapid six-degree temperature increase is what some scientists believe to have brought about the mass extinction that marked the end of the Permian period some 250 million years ago. That six-degree increase is estimated to have taken some 10,000 years to occur and it took life on Earth tens of millions of years to recover from that catastrophic episode of global warming. Back then the climate change was probably caused by volcanic activity: this time the warming is caused by power stations, deforestation, cars, farms, and factories. If we don’t do something about these sources of global-warming gases very quickly, then we could, the most recent projections show, trigger six degrees of warming not over 10,000 years, but in less than a century.

Temperatures even three degrees above the

pre–industrial average have not been seen

since the Pliocene period, some three million

years ago. At that time sea levels were up

to 25 metres higher than now.

At the moment this appears to be where we are heading. Emissions scenarios prepared in 2000 set out different possible future emissions levels based on different assumptions about economic growth and the uptake of new technology. And yet in 2005, 2006 and 2007 the world’s emissions of greenhouse gases were above the line set out in the worst-case scenario. We have arrived at the brink of potential disaster, and yet we still accelerate towards the edge.

Glaciers are very sensitive to climate change and as the average global temperature rises glacier retreat is underway worldwide. At Glacier Bay National Park, Alaska, there has been dramatic glacier shrinkage. On the left a steamship sails toward the Muir Glacier in 1902. From the same viewpoint in 2005 the glacier has disappeared.

Nevertheless there is some cause to be encouraged. We still have some time to minimize the impact of the increases in carbon-dioxide levels, but not much. For the industrialized developed countries, a cut in carbon-dioxide pollution of about 40 per cent by 2020 might place the world on an emissions reductions path that could avoid the worst effects of what lies ahead. That is not to say that the impact we have on the world could or must be reduced to zero by then, but rather that this is the direction we should be travelling in. What is certain is that this is mostly the opposite direction to that travelled by humanity today.

The evidence which shows Man-made impact on the climate system recently became the subject of fierce debate. Those who are sceptical that humanity’s activities have caused climate change made an all-out assault on the evidence base in the run-up to the UN Conference on Climate Change in Copenhagen at which I spoke. The row had an alarming effect on public opinion, and being so close to it I could see that it was a deliberate attempt to dampen the justified concerns about the climate change threat that the Media had been increasingly reporting in recent years. But whether you choose to believe the sceptics rather than the vast body of evidence that now exists, climate change is not the only large-scale ecological challenge that we face. Alongside changes to our planet’s atmosphere, the activities of our single species have caused an unprecedented assault on the fabric of life.