Sir

Gwyn Prins and Steve Rayner are effective in reiterating the Kyoto Protocol's flaws, in their Commentary 'Time to ditch Kyoto' (Nature 449,973–975; 2007). But their language is unnecessarily negative and they do not deliver a clear, credible alternative.

The Kyoto Protocol is not enough to create the low-emissions transformation in the global economy that is required to tackle the climate problem successfully. But it is already resulting in low-carbon investment and emissions reduction, and is a step towards an effective global treaty. In focusing on the name and arguing that it should be ditched, the authors overlook the potential of a 'Kyoto phase 2' that builds on this approach.

Their call for investment in developing technologies as a cornerstone of our response is right, but it doesn't address the important question of how to achieve it. It takes 20 years for new technologies to get to market — time we do not have. What we need are tools (such as a cost for carbon through market incentives and emissions trading) that facilitate rapid uptake of existing clean technologies. Investment in low-carbon technologies and cap-and-trade measures are two sides of the same coin: to achieve one requires the other. The market is awash with investment funds — good policy is needed to unlock them.

Trying to build a new agreement from the ground up, or hoping for a bottom-up solution to emerge from a mix of domestic responses, simply risks yet another decade of delay, diplomatic wrangling and nationalistic plea bargains while the climate system moves towards catastrophic tipping points.

As Winston Churchill said: “It's not enough that we do our best; sometimes we have to do what's required.” That will also hold at the meetings in Bali next month, in Poland next year and in Copenhagen at the 2009 United Nations conference. Pointing out the treaty's inadequacies is all very well, but the harder and more vital job is building on it to achieve a more effective and adequate one.