As we approach the climate change negotiations in Copenhagen, one thing is clear: for millions of people around the world climate change is not simply a future threat, it is a current reality.

In my role as the United Kingdom’s International Development Secretary, I’ve met people around the world who are living with the consequences of climate change – from families in Bangladesh forced to leave their flooded homes, to women in parts of Ethiopia who are walking further each year to collect water for their families.

In Rwanda, where so many people depend on a successful harvest, increased variability in the quantity and timing of the rains is having a significant impact on the economy, but more pressingly perhaps on the livelihoods of the poorest and most vulnerable.

These people are the least responsible for climate change, yet they are already most affected by it. As we look to the future it is clear that climate change will increasingly hit poor people hardest.

By 2020, some countries across Africa could see the yields from rain-fed agriculture fall by a half. By 2035, the Himalayan glaciers, which provide water for up to 1.5 billion people across Asia, could disappear. By 2080, an extra 400 million people could be exposed to the threat of malaria.

Climate change threatens to make poverty the future for millions of people.  That is why the government of the United Kingdom believes that the world has not only a common interest, but also a moral responsibility to people in the most vulnerable countries, to secure a fair deal on climate change.

To keep global temperature rises below 2 degrees centigrade will mean nothing less than a 50 per cent reduction in global emissions by 2050, compared to 1990 levels.

This will require a firm commitment from rich nations to significant cuts in emissions – for developed countries do bear the greatest responsibility for the emissions we have seen over the past century.

A deal will also need to involve developing countries – because the greatest growth in emissions over coming decades will be in such countries.

At the same time we must agree a strong deal on climate finance, to help developing countries both adapt to the now-inevitable effects of climate change, and get their economies on a low-carbon path to growth.

The British Prime Minister, Gordon Brown, has led the way in calling for around $100 billion per year by 2020 – drawn from a combination of public finance and carbon markets - to help developing countries develop clean energy, adapt to the effects of climate change and protect forests.

Some of this climate finance can legitimately come from official development assistance, where investment helps to both fight poverty and tackle climate change.

But a ceiling should be placed on the proportion of development assistance that goes towards climate funding.
Without such a commitment, there is a risk that governments will divert a large proportion of aid budgets to fulfil their commitments on climate change, diverting money away from healthcare, education and humanitarian assistance.

We cannot allow a choice to exist between fighting poverty and tackling climate change, and that is why the UK has set a limit of up to ten per cent of development assistance that can be invested in climate funding.

Our support is already helping communities to tackle climate change and lift themselves out of poverty.

In Rwanda we are working with the Government and other partners to better understand the impact that Climate Change will have on the country and its communities. And to use this understanding to plan for the future, to help protect the economy and the most vulnerable from these impacts.

In the run-up to the Copenhagen meetings we have also provided support to ensure that developing countries have a strong, coherent voice at the table.

The next few weeks represent not a window of opportunity, but a window of necessity in our efforts to strike a climate deal to protect the lives and livelihoods of this and future generations.

The author is the UK Secretary of State for International Development