The Intergovernmental Panel on Climate Change has released the most comprehensive ever study on global warming, prepared by more than 200 scientists over two years.
The landmark report concludes that if the world continues to emit greenhouse gases at current rates, we will face warming of more than 2C, compared to pre-industrial levels, within as little as two to three decades.
This is hugely significant because all countries have agreed that temperature rises should be restricted to no more than 2C, thus increasing prospects of preventing so-called dangerous or runaway climate change. The study also concludes that it is "extremely likely" (at least 95 per cent probability) that human activity has caused most of the increase in global temperature in recent decades.
The report downplays the fact that global average surface temperatures have risen more slowly in the past 15 years, contrary to earlier IPCC predictions, saying there were substantial natural variations that masked a long-term warming trend.
This point will nonetheless be seized upon by climate change sceptics.
Despite the controversy it will cause with sceptics, the IPCC report will be welcomed by many across the world, and comes during a period when it may seem hard not to be pessimistic about the global battle to manage the huge risks of climate change. For instance, the last annual UN international climate change summit in Doha in December made only modest progress toward securing a comprehensive, global deal.
Moreover, climate change sceptics appear to be winning the battle for public opinion across much of the world.
This month, for instance, one study showed that the percentage of British people who do not think the world's climate is changing had increased by a staggering four-fold in less than a decade.
However, far from being the hopeless situation some suggest, there are signs that we may be reaching a point when the tide turns on tackling climate change. To be sure, much more needs to be done, but if one takes a step back and examines what is already happening at national and sub-national level across the world, a relatively encouraging picture emerges.
That is, domestic laws and regulations to address climate change are being passed at an increasing rate - in stark contrast to the pace of progress in UN-driven international negotiations. In 2012 alone, as described in a report published by GLOBE International, 32 of 33 surveyed countries (which account for more than 85 per cent of global greenhouse gas emissions), including the United States and China, have introduced or are progressing significant climate or related legislation and regulation.
This is nothing less than a "game-changing" development:
China, after the publication of its 12th five-year plan in 2011, has proceeded with more detailed implementation guidelines including rules for its emissions trading pilots, progress with drafting its climate change law and publication of an energy white paper. Moreover, at the end of October last year, sub-national legislation was passed in Shenzhen to tackle climate change - the first such legislation in China.
Mexico has passed a general law on climate change - a comprehensive legislative framework packaged together with the first Redd+ readiness legislation to tackle deforestation.
South Korea passed legislation to begin a nationwide emissions trading scheme by 2015.
South Africa has proposed a carbon tax.
There has also been progress in the developed world. For instance, the European Union passed a new directive on energy efficiency, and Germany strengthened legislation relating to CCS and energy efficiency.
As these examples underline, it is mainly developing countries, which will provide the motor of global economic growth in coming decades, which are leading this drive. Many are concluding it is in their national interest to reduce greenhouse gas emissions by embracing low-carbon growth and development, and to better prepare for the impact of climate change.
They see that expanding domestic sources of renewable energy not only reduces emissions but also increases energy security by reducing reliance on imported fossil fuels. Reducing energy demand through greater efficiency reduces costs and increases competitiveness. Improving resilience to the impacts of climate change also makes sound economic sense.
Many governments and companies have recognised that a green race has started, and they are determined to compete. They also acknowledge that, over time, those that produce in "dirty" ways will be increasingly likely to face border adjustment mechanisms which take account of the subsidy associated with their taking advantage of any unpriced pollution.
It follows, therefore, that advancing domestic legislation on climate change, and experiencing the co-benefits of reducing emissions, is a crucial building block to help create the political conditions to enable a comprehensive, global climate agreement to be reached. Domestic laws give clear signals about direction of policy, increasing confidence and reducing uncertainty, particularly for the private sector which can drive low-carbon economic growth.
With negotiations on a post-2020 comprehensive global deal scheduled to conclude in 2015, it is unlikely that an agreement, with necessary ambition, will be reached unless more domestic frameworks are in place in key countries. Sound domestic actions enhance the prospects of international action, and better international prospects enhance domestic actions.
Given this outlook, and as negotiators prepare for the next annual UN climate change summit in Poland in November, a potential danger is that some countries might lower their long-term ambition.
This would be ill-timed. Indeed, now is the right moment for countries to invest more in tackling climate change, in order to help expedite the creation of conditions on the ground that will enable a comprehensive global treaty to be reached.