Be in no doubt. Climate change is not tomorrow's future menace. It is today's growing catastrophe. In Copenhagen next month, a meaningful deal must be secured if we are to have any hope of avoiding catastrophe.

This very human catastrophe is already being felt in parts of the world. This year, entire communities in Bangladesh are being forced to leave their homes due to rising sea levels; women in drought-ridden parts of Ethiopia have to walk five miles a day to collect water; and natural disasters are occurring with increasing frequency and ever more devastating results.

Climate change threatens us all. If we fail to bring it under control in the next decade we may move past the point of no return. This is a defining political test of our generation. Less than one degree of global warming since the industrial revolution has caused dangerous changes to our world.

Last month, the government of the Maldives held a cabinet meeting underwater to illustrate the stark reality facing the nation. The meeting caused a media sensation internationally. It was a lighthearted event with a deadly serious message: if climate change is not addressed, these beautiful islands will slowly slip into the Indian Ocean.

This week, the Maldives is hosting a conference of climate-vulnerable developing countries. The conference aims to thrash out a common position among the most vulnerable nations ahead of the Copenhagen meeting in December.

Britain stands shoulder to shoulder with the Maldives and all vulnerable countries. We are working to ensure the voices of the people who will be hit first and hardest by climate change are heard around the negotiating table.

Copenhagen must secure a deal that sees rich countries shouldering their fair share of the burden of controlling climate change. This means tough targets on their own emissions but also an agreement on funding to help developing countries pursue green growth and cope with the impacts of climate change.

This will mean helping to end the deforestation that sees 8m trees lost every day, governments working with the private sector to secure large investments in green industries and a strong commitment to renewable energy, to make renewables cheaper than fossil fuel.

A fair deal at Copenhagen also means that climate change funding is not plundered from existing aid budgets but should be new, additional finance. It is vital that the developing world has a strong, coherent voice at the table. The rich world must take the lead in cutting emissions and providing sufficient funds for developing countries. They, however, also have responsibilities. Developing nations need to grow, but their economic growth must be green.

To that end, the Maldives has signed an agreement to build a 75MW wind farm, which will power the capital, Mal, the international airport and 24 luxury tourist resorts. This project will cut CO2 emissions by 25%. It is due to be operational in 20 months. If a small, developing country can make this rapid shift to renewables, there can be little excuse for richer nations to drag their feet.

Copenhagen is a moment of necessity. We must agree a credible, long-term deal that is fair and equitable. One that merely protects the interests of the rich will tell the world that the leaders of 2009 lacked the political will and moral conviction to help those whose lives will be blighted by climate change.

We need to use these last 28 days before Copenhagen to ensure that all parties are in a position to work towards a deal that will stand alongside the Geneva conventions and the UN charter as a defining document for humanity. Douglas Alexander is international development secretary; Mohamed Nasheed is the president of the Maldives