The Big Debate: Should we aim to stop climate change or adapt to it?

Is preventing climate change the most important challenge facing humanity?

Tackling climate change is certainly the most important task before us, but we can't stop it happening completely. It's already taking place as a result of our past emissions of carbon dioxide and other, polluting greenhouse gases.

What do you mean?

The world, on average, is about 0.75C warmer than it was a century ago and even that apparently small increase is having dramatic effects around the world. Since the Fifties, the Arctic icecap has shrunk by a quarter (in summer) and lost almost half its thickness. Whole Antarctic ice sheets are also disintegrating. Five years ago, the Larsen B shelf, a 200m-thick shelf larger than Luxembourg, shattered in little more than a month. Even mountain glaciers are melting worldwide. A quarter of those in Tibet have already disappeared.

Sea levels are rising, summers are getting longer, wildlife species are moving up mountains and towards the poles, storms are becoming heavier and more frequent, and the global area affected by drought has doubled since 1970.

And closer to home?

The effects are also showing in Britain. Extreme monthly temperatures that used to occur every 100 years now happen every 20. Spring keeps starting earlier, as the profusion of flowers in what used to be winter demonstrates. Two thirds of the North Sea's fish species have shifted further North, or plunged to greater depths, to get away from warming waters. And though the recent floods can't be conclusively blamed on climate change, increasing inundations have long been predicted as the climate changes.

Can we at least stop it now?

Unfortunately not. Greenhouse gases stay in the atmosphere for a long time and the oceans take even longer to heat up and cool down, so great inertia is built in to the system. Even if we stopped all our emissions now, the world would still go on heating up for at least the next 30-40 years, increasing temperatures by another 0.6C. And, of course, we can't simply stop the emissions because economies and societies everywhere would collapse if they abruptly stopped burning the fossil fuels that emit carbon dioxide. The best we can do is reduce their use as fast as possible and target the biggest sources of emissions, which matter most. However, this means the world is inevitably going to warm up even more.

How big is the challenge?

Mind-bogglingly so. Let's just take a few examples. The official Intergovernmental Panel on Climate Change says that, as soon as 2020, yields from rain-dependent farming in some African countries could be reduced by half, while up to 250 million people in Africa will be increasingly short of water.

More than a billion people in South America and Asia face losing their water supplies as the mountain glaciers on which they depend melt. And many of the world's biggest cities ­ and much of its industry ­ are on low, coastal ground and so are highly vulnerable to rising seas. Four fifths of China's GDP, for example, is produced in three low-lying deltas ­ those of the Yangtze, Yellow and Sui Jiang rivers ­ where flooding is expected to increase five or sixfold over the next few decades.

Can we adapt?

We're going to have to learn to adapt to a changing climate ­ and fast ­ even if we do all we can to cut emissions. Such "adaptation", as it's called, is probably an even greater challenge than trying to bring climate change under control, but so far it's received far less attention. Countries such as the Maldives and the Netherlands have begun building estimates of rising sea levels into their sea defences. And, at home, it's now accepted that there will have to be a new Thames Barrier to protect London, but this is only the smallest of starts.

Is this mainly a problem for the developing world?

Yes and no. Generally speaking, the worst effects of climate change will be in poor countries and will hit their poorest people hardest. This is particularly unfair because these people are the least responsible for climate change (emitting far less pollution per person than we do) and are the least able to adapt because of their poverty.

But rich countries are far from immune from disaster, as the devastation brought by Hurricane Katrina in the United States and the recent floods in the United Kingdom showed. In fact, flooding here is expected to increase tenfold this century.

What measures do we need to put in place?

A whole host, ranging from increasing flood defences to the development of crops that resist drought and floods; from conserving water supplies to preserving forests (and planting new ones) because these catch rainfall; from enormous projects, such as protecting those flood-prone Chinese cities, to the apparently mundane, such as improving gutters on British homes to cope with more torrential rainfall.

Indeed, the Government's Housing Green Paper spelt out the need for builders of all new housing developments to seek advice on flood risk from the Environment Agency.

There will also have to be greatly increased financial assistance from rich to poor countries and a new level of international cooperation.

Does all this mean we should concentrate on adapting to climate change rather than reducing it?

Absolutely not! It's going to be hard enough to adapt as it is and if the impact of climate change increases much more, it will become impossible.

The growing consensus is that we'll only be able to cope if we can keep the warming to 2C. After that point, dangerous, even unstoppable, climate change becomes more and more likely. For example, the Greenland and West Antarctic ice sheets may melt, eventually raising sea levels by nearly 12m.

With 0.75C of warming having happened already and ­ at the very least ­ another 0.6C inevitably to come, we're getting very close to the danger point. We have to act to reduce climate change and also adapt to its consequences. We must do both at the same time ­ and with the utmost urgency.

What is HSBC doing to help? Find out more at www.hsbc.com/cr

The physical impacts of climate change may already be having serious consequences, both in the UK and elsewhere. HSBC believes it can play an important role in advising its employees and customers on how best to adapt to a changing climate, be that minimising the adverse effects of extreme weather events or mitigating climate change risk through the development and implementation of renewable energy technologies.

Through the recently launched HSBC Climate Partnership, we hope to understand better the effects of and potential solutions to the impacts of climate change on people, forests, water and cities. The five-year £50 million partnership brings together HSBC, The Climate Group, Earthwatch Institute, Smithsonian Tropical Research Institute and WWF.

In 2006, HSBC and WWF funded the extension of the Yorkshire Wildlife Trust's Potteric Carr wetland, which is designed to store flood water in the case of extreme weather events. Earlier this month, the severe weather in the UK caused 15 rivers to burst their banks, flooding 27,000 homes and affecting 5,000 businesses. The extension of the wetland reserve acted as a natural flood defence by providing an additional 500,000m ³ of flood water storage, which proved critical in the extreme conditions and caused the South Doncaster flood waters to spill safely over onto the reserve.

As one of the world's largest financial institutions, HSBC believes there is both a need to reduce the short-term physical impacts of climate change through projects such as Potteric Carr and also ensure that our operations ­ and indeed our 125 million customers ­ are able to adapt to the inevitable consequences of climate change.