Six years later the IPCC repeated the trick: its 2007 fourth assessment report said much the same, while increasing the confidence in its conclusions and loosening the constraints on the likely effects. This time the world seemed ready to listen, and by 2009 world leaders have pledged to negotiate a new global climate deal that will go some way to addressing the need to cut soaring carbon emissions. Scientists warn that the years of inaction since the IPCC issued its earlier warnings could prove costly. Emissions have continued to rise, worsening the inevitable climate problems and making it more awkward for politicians to pledge to slow a rapidly accelerating runaway train. And it has also made it more difficult for the world to meet the UN's millennium development goals.
Ban Ki-moon, UN secretary general, has warned that "climate change is a serious threat to development everywhere. Indeed, the adverse impacts of climate change could undo much of the investment made to achieve the millennium development goals." …Sha Zukang, UN under-secretary general for economic and social affairs, told the same meeting that "climate change is fundamentally a sustainable development challenge". To make progress, he said it would be necessary to "bridge the divide between actors on the environment and on development which, despite our past efforts, continues to exist."
…It is difficult to be precise about the likely impacts on specific locations. Africa's climate is complex and there is little hard data on the current conditions to feed into the models. Most global models predict long-term effects, from 2050 onwards, and only in large geographical chunks more than 100 miles across. This means the most useful predictions, such as what might happen to a particular country in the next decade or so, are the most uncertain. Nevertheless, some impacts can be predicted with some confidence. The most obvious is the effect on agriculture and food supplies. As well as the problems caused by more heavy rains and drought, rises in temperature are expected to have negative impacts on crop yields and areas of available cultivatable land…..