LONDON

At the start of my political career someone once warned me about the danger in politics of “benign neglect” — good intentions being obviated by lack of focus. That is the danger we face today on climate change.

Next month, at a U.N. summit in Copenhagen, decisions will be taken that determine the future of the planet. But a deal in Copenhagen is in danger; and the greatest danger of all is that amid the competing priorities of economic recovery, Afghanistan and nuclear non-proliferation we fail to see the problem until it is too late. To tip the balance, the British government has begun a new diplomatic push with European colleagues from France, Finland, Denmark and Sweden. We are working on four fronts.

First, climate change needs to be taken out of the “environment” box. A deal is not just desirable, but an imperative for national security and sustained economic recovery over the medium term, on a par with the fight against terrorism. High oil and food prices were a trigger for the current economic crisis, building up global financial imbalances and pushing up interest rates. The resource crunch is the second parent of the crisis alongside the credit crunch. Climate change will result in mass migration, drought and water shortages, causing tension and conflict within and between nations. Global warming may not be on the U.N. Security Council agenda now, but it will be in future if we do not wean ourselves off carbon.

Second, we need a deal that passes a simple test: whether it is consistent with living in a world where temperatures rise by no more than 2 degrees. Most diplomatic negotiations involve compromise. This will be no different. But the one area we should not trade off is the level of ambition in a Copenhagen deal. Climate change is a non-linear phenomenon. Beyond 2 degrees and scientists warn us that the effects on the planet could be catastrophic. Worse still, there is a sharply increased risk these effects will create vicious cycles that cause runaway climate change, such as the melting of the permafrost.

Third, the biggest threat to a deal in Copenhagen is about finding a fair distribution of responsibility between developing and developed nations. The rich world bears historical responsibility for the problem and has much higher current per-capita emissions. But the developing world will be responsible for the majority of emissions growth in the future, and will suffer the greatest costs from climate change.

The way through this is clear, but challenging to achieve. The developed world needs to make ambitious cuts in its emissions equivalent to 25 percent to 40 percent by 2020. It needs to provide the finance and technology to let poorer countries develop low-carbon energy, and adapt to the climate change already in train. In return, poorer countries cannot be expected, at current levels of development, to cut overall levels of emissions; but they must make commitments to make verifiable shifts in their emissions profile from the business as usual of high carbon growth.

Fourth, we need a shift in tactics. Climate change is not a zero-sum game and we should not adopt zero-sum tactics. If we wait until the negotiations in Copenhagen to reveal our hand in order to squeeze the best deal out of other countries, the deal will either not happen or be insufficiently ambitious. If poor countries know that rich countries are prepared to shoulder responsibility, I believe that they will step up to the mark. We need to generate trust and momentum in the run-up to Copenhagen. That is the significance of the decision of the new Japanese government to move from an 8 percent reduction in emissions by 2020 on 1990 levels to a 25 percent reduction. We need more game-changing interventions. As British Prime Minister Gordon Brown has argued, we need to generate a finance offer — $100 billion annually by 2020 — to poorer countries to let them begin the transition to low-carbon development and adaptation.

The U.K. is determined to show leadership on this issue. We are the first country to set a legally binding target to cut emissions by 34 percent by 2020 on 1990 levels toward an 80 percent cut by 2050. But the U.K. can have more impact as part of an E.U. mobilization.

The E.U. has the world’s first carbon market that transfers funds to poorer countries where emissions reductions are most cost-effective. The E.U. is the biggest single market in the world. When it sets standards for cars or fridges it has the power to drive innovation. The E.U. is the second-biggest aid donor in the world. When it puts together a climate-finance package, it can leverage action from developing countries. And the E.U. thrives on big projects: peace and reconciliation after WWII, the single market, the euro and enlargement. The next big project for the E.U. — the environmental union — is to be the catalyst for a world beyond carbon.

Climate change involves science, economics and technology. But now a deal depends on politics. We need a fresh approach, and we need it soon.

David Miliband is the British foreign secretary. His brother, Edward Miliband, is the U.K.’s minister for energy and climate change.