In an earlier column ("Slow burn", October 6, 2013), I had commented on the implications of the first volume of the fifth assessment for India. The second volume has much more direct focus on regional consequences. While the geographic distinctions are confined to continents, more disaggregated assessments are made on some issues. Even without going down to national or sub-national levels, though, the continental impact assessments provide substantial evidence of significant impacts on India, some of which will undoubtedly reinforce and aggravate already serious structural problems relating to water supply and food production. The next volume of the report will address mitigation and adaptation strategies for different impact zones, but, clearly, every country and even sub-national entities will have to think through these in the larger context of their overall development strategies.

Chapter 24 of the report addresses Asian impacts. Towards the end of the chapter, there is a set of frequently asked questions, which, as might be expected, cover the issues of water availability, food security and health. As regards the first, there is a general perception that climate change is having a significant impact on rainfall patterns, with India being particularly vulnerable to decreasing precipitation. Interestingly, the report, while admitting to the possibility of a climate change-precipitation linkage, says this is a conclusion in which existing knowledge reposes low confidence, particularly at sub-regional level. In other words, even if there is a trend decline in rainfall, it may be due to factors other than climate change.

Notwithstanding this, the report warns of increasing water stress across Asia. This will partly be from demand-side pressures - increasing populations, to which India and South Asia generally will be the predominant contributors and rising income levels - but also from constrained availability. Presumably, surface water will evaporate more rapidly, while groundwater systems in areas in which rivers are fed by melting snow will face depletion from receding glaciers. This is a situation in which incentives to overuse water because of both direct and indirect subsidies (to power, for example) will interact with the environmental drivers to cause a vicious spiral.

In contrast, the report says there is a high level of confidence in the adverse impact of climate change on food security. While the impact is not uniform - in some areas, food productivity may increase because of warming (for example, Central Asia) - in others, including the Gangetic plain, the impact will be adverse. Declining food productivity in India will be aggravated by the rising sea levels, which are an inevitable consequence of climate change and threaten the thickly populated coastal regions of Asia in a variety of ways. However, specifically on the agricultural front, the intrusion of sea water will reduce the availability of arable land, primarily through increased salinity levels. In short, rising populations and consumption levels are going to go head-on against decreasing food productivity in the South Asian region. In the absence of effective mitigation measures, which reorient cultivation patterns and water intensity, food inflation - which is already entrenched - will become a permanent component of the macroeconomic environment. It is not clear, though, that global food availability will decline; in any case, for countries like India, reliance on international trade in food will probably increase.

Apart from the impact on land availability and productivity, the impact on coastal ecosystems will also be significant. Seafood is obviously an important source of protein for coastal populations; the availability of this will be impacted as breeding areas for various species either wither away or shift elsewhere. Even the productivity of inland water sources is presumably going to be impacted by changing conditions.

On the health front, the report says there is high confidence in the current state of knowledge that significant impacts will manifest. Heatwaves are likely to become both more frequent and more intense, resulting in a surge in morbidity, particularly among vulnerable urban populations. With medium confidence, the report warns of cholera outbreaks in Bangladesh, for example, which could spread widely in hospitable climatic conditions. The threat of Japanese encephalitis increases in the Himalayan region. Other parts of Asia are also vulnerable to increases in morbidity. In particular, the geographic range of several vector-borne diseases will increase because of warming.

The overall approach of the IPCC has been to qualify all its analytical findings with the level of confidence that the current state of knowledge affords. All the assessments referred to above, except the sub-regional link between climate change and precipitation, are at either medium or high confidence. Risk assessments have to be built into policy decisions, so to the extent that evidence suggests that these risks are high, no government can afford to ignore them. But, in shaping effective mitigation strategies, it is important to embed them into a wider short-term and long-term macroeconomic and development policy framework.

The first volume of the fifth assessment suggested that the bulk of the predicted impacts would manifest most strongly in the second half of this century. In terms of appetite for implementing costly mitigation measures, this assessment causes a schism between countries with relatively old and relatively young populations. In effect, the most realistic options for countries like India are now based on self-reliance. Mitigation of the larger global threat obviously cannot be achieved by individual countries. Only local mitigation and, most pragmatically, adaptation can be achieved by countries acting alone.

The report provides a summary risk assessment, based on current efforts at adaptation and more aggressive responses. On some of these fronts, more effort can apparently reduce risks considerably. On others, most particularly on the agricultural productivity front, even intense efforts at adaptation still leave the continent - and, presumably, the subcontinent - extremely vulnerable, with the risks only increasing over time. Clearly, these are issues that will become increasingly central to the overall economic policy debate.