The world must start adapting now to a very different, much hotter tomorrow, one in which business as usual policies and practices will simply not suffice. The extreme weather events over the past two years provide a foretaste of what is to come. But dealing with more frequent and intense disasters (to use an apt metaphor) will be only the tip of the iceberg.

Climate change presents unique challenges, and its scale, pace and complexity defy easy solutions. Governments must contend with impacts ranging from increasingly intense storms, to crop-threatening changes in seasonal rainfall, to sea level encroachment on coastal cities and deltas. Public officials are also hampered by debilitating uncertainty as to how climate impacts will unfold within their borders. Ghana, for example, must accommodate a huge range of predicted future rainfall – from 60% less than today by 2050 to 49% more – as it develops its water and agriculture sectors.

The decades-long timeline over which climate change will evolve also presents a conundrum for decision makers used to operating in a five-year election cycle. Difficult trade-offs will be necessary as governments seek to balance short and term long needs (should they vaccinate children or shore up coastal defenses?)

Finally, climate change will exacerbate the vulnerability of the poor and marginalized, both among and within countries. A category five cyclone that hits Bangladesh has a very different impact than one that strikes Brisbane.

Given these myriad challenges, climate change demands a different approach to decision making, according to a major new report by the UN Development Programme, the UN Environment Programme, the World Bank and the World Resources Institute. The World Resources Report 2010-2011: Decision Making in a Changing Climate focuses not on what policies governments should adopt to prepare for climate change (already well-traveled ground) but on how to make effective and durable adaptation decisions. Targeted at national governments, it calls on decision makers to incorporate climate risks into plans and policies for critical sectors such as coastal planning, agriculture, water, forestry and power generation. Failure to do so, it warns, will likely leave poor communities more vulnerable and undermine expensive investments in infrastructure such as dams, seawalls, bridges and coastal settlements.

Drawing on the policy expertise and field experience of more than 100 contributors in 36 countries, the report highlights innovative early approaches to adaptation from the developing world. These include 12 detailed case studies that examine how developing country governments are tackling obstacles to integrate climate risks into short and long-term decision making.

Many of these approaches employ policies and tools already in common use, and complement, rather than compete with, development needs and aspirations. Indeed, we argue that integrating risk management across government can provide a unique opportunity to reduce overall poverty and vulnerability.

The report urges developing countries (and donors) to focus efforts in five key areas. While not new priorities, these take on added urgency in the face of looming climate risks.

Since adaptation policies will inevitably involve compromises, winners and losers, we argue that active public engagement in deciding on and implementing adaptation plans and policies is a prerequisite for success. The report also calls on governments (with donor support) to: collect and distribute accessible climate information to affected populations; establish institutions to coordinate and prioritize climate risks in planning and decision making across government; and use decision support tools such as hazard maps and scenario planning to assess risks and vulnerabilities and choose adaptation policies. Finally, we urge developing countries in the frontline of climate impacts to build the human and technical capacity to prepare for a warmer world, and donors to design new, flexible, long-term support mechanisms.

Climate change will test the ability of governments to lead as never before. Given the difficult trade-offs involved, and the scale of resources needed, the decisions that climate change imposes on governments are more political than technical. How decision makers and societies make these choices will determine how well they adapt to a changing climate, and shape the world our children and grandchildren inherit.