The Cancun climate change summit is taking place in the context of the summer's extraordinary floods in Asia and record high average temperatures over the whole world (with drought in other parts of Asia and southern Africa).
Moreover, with the snows melting last year on the Andes, as on high mountains everywhere, the Amazon had record-high and record-low levels.
While the "urgency to act" is thus growing in some quarters, the prospects for a comprehensive deal in Mexico are slim.
The central problem is that there remains slow progress and uneven elite and popular support in many countries for the United Nations objective of achieving within the next 20 to 30 years the necessary reductions in overall emissions of greenhouse gases.
At the Cancun preparatory meeting in Tianjin in October, little progress was apparently made amid widely reported public disagreements between the United States and China. With Washington accusing Beijing of reneging on its commitments to transparency under last year's Copenhagen Accord, China asserted that the US was not reducing its greenhouse gases.
While even a significant US-China rapprochement will probably not be enough to secure a comprehensive deal at Cancun, such a development would undoubtedly increase the prospects for a new agreement next year and beyond. But, what are the chances of Beijing and Washington moving closer in the months to come?
To answer this question, it is imperative to understand the Chinese perspective on climate change, especially as the country is now the largest emitter of greenhouse gases in the world. While there has been major discussion in recent years about US climate change policy, much less attention has focused on that of China and the reasons why it views the problems of curbing global warming differently from the West.
For instance, in discussions in the West about how to avoid dangerous climate change, two numbers are especially prominent - 450 parts per million and 2C. These are, respectively, the upper "safe" concentration of carbon dioxide in the atmosphere, and the upper "safe" limit of average global temperature increase. The fear is that if we exceed either, the climate will pass an irreversible tipping point.
In my most recent visits to China, including last month, I have heard some very different numbers being debated.
China is absolutely committed to political stability and that stability depends on economic growth. Over the next 40 years, it forecasts that its gross domestic product will increase by a factor of six. The driving force of this enormous growth will be fossil fuels, in particular coal.
China's stated policy is to increase the total output of its coal-fired electricity generation while improving efficiency. This is its only significant target in relation to energy and climate change.
China, in other words, is not committed to limiting emissions so as not to exceed any particular target for the global CO2 concentration.
This is not to say, however, that China does not regard the climate change issue seriously. Legislation will soon also be introduced to make compulsory the reductions in emissions per unit of energy by up to 40 per cent and also to expand low carbon supplies by up to 15 per cent of the total, including solar, wind, hydro and nuclear fission.
Moreover, authorities are already encouraging industries to reduce emissions by using carbon trading at five regional centres. Beijing is also considering a mandatory carbon-trading scheme as part of its 12th five-year plan, to be published next year.
Despite these efforts, the country's booming overall emissions will contribute significantly to atmospheric CO2. Indeed, this overall picture is consistent with estimates last year by the Beijing Climate Centre that by 2050 total Chinese greenhouse gas emissions may be more than double the current levels.
Climate models indicate that this continued growth in emissions will lead to atmospheric concentrations of the gases equivalent to about 600ppm and global land temperatures in excess of 3C-4C by 2100.
These are staggering numbers compared with those being discussed in the West. The key question that arises is whether there is anything the rest of the world can do to avoid the risk of dangerous climate change that these Chinese numbers imply?
I believe there are reasons to be hopeful. The main way that China can limit its emissions will be to improve the efficiency of its coal-fired power stations, adopt carbon capture and storage, and expand nuclear power.
Developed countries, including the US, can encourage and facilitate this transition by providing China with substantial technological assistance. But first, Western nations must commit to making deep cuts in their own emissions - in the order of at least 80 per cent - before 2050, conditional on China doing so after 2050 as its energy efficiency, renewable and nuclear programmes become effective.
As ambitious as it may seem, an international agreement along these lines next year or beyond is a credible goal (although it would most likely need to be facilitated outside of the UN process), for at least two reasons.
Firstly, because China has a long-term financial interest in collaborating with the West. And secondly because - as I have seen in meteorology and in plasma physics - China has a good track record in delivering on advanced technology projects and sticking to international agreements.
For those, like myself, who believe that global warming is the greatest danger to humanity in the 21st century, it is to be hoped that all countries will show the ambition and imagination needed to move towards a comprehensive and effective deal in Mexico.
With a growing urgency to act, we simply cannot afford to see the shambles of Copenhagen repeated in Cancun.
Lord Hunt is former director-general of the UK Met Office, now a visiting professor at Delft University in the Netherlands.
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