TS.5.4 Perspectives on climate change and sustainability
Future vulnerability depends not only on climate change but also on development pathway.
An important advance since the Third Assessment has been the completion of impacts studies for a range of different development pathways, taking into account not only projected climate change but also projected social and economic changes. Most have been based on characterisations of population and income levels drawn from the SRES scenarios [2.4].
These studies show that the projected impacts of climate change can vary greatly due to the development pathway assumed. For example, there may be large differences in regional population, income and technological development under alternative scenarios, which are often a strong determinant of the level of vulnerability to climate change [2.4].
To illustrate, Figure TS.18 shows estimates from a recent study of the number of people projected to be at risk of coastal flooding each year under different assumptions of socio-economic development. This indicates that the projected number of people affected is considerably greater under the A2-type scenario of development (characterised by relatively low per capita income and large population growth) than under other SRES futures [T20.6]. This difference is largely explained, not by differences in changes of climate, but by differences in vulnerability [T6.6].
Figure TS.18. Results from a recent study showing estimated millions of people per annum at risk globally in the 2080s from coastal flooding. Blue bars: numbers at risk without sea-level rise; purple bars: numbers at risk with sea-level rise. [T6.6]
Vulnerability to climate change can be exacerbated by the presence of other stresses.
Non-climate stresses can increase vulnerability to climate change by reducing resilience and can also reduce adaptive capacity because of resource deployment to competing needs. For example, current stresses on some coral reefs include marine pollution and chemical runoff from agriculture as well as increases in water temperature and ocean acidification. Vulnerable regions face multiple stresses that affect their exposure and sensitivity as well as their capacity to adapt. These stresses arise from, for example, current climate hazards, poverty and unequal access to resources, food insecurity, trends in economic globalisation, conflict, and incidence of disease such as HIV/AIDS [7.4, 8.3, 17.3, 20.3].
Climate change itself can produce its own set of multiple stresses in some locations because the physical manifestations of the impacts of climate change are so diverse [9.4.8]. For example, more variable rainfall implies more frequent droughts and more frequent episodes of intense rainfall, whilst sea-level rise may bring coastal flooding to areas already experiencing more frequent wind storm. In such cases, total vulnerability to climate change is greater than the sum of the vulnerabilities to specific impacts considered one at a time in isolation (very high confidence) [20.7.2].
Climate change will very likely impede nations’ abilities to achieve sustainable development pathways, as measured, for example, as long-term progress towards the Millennium Development Goals.
Following the lead of the TAR, this Report has adopted the Bruntland Commission definition of sustainable development: “development that meets the needs of the present without compromising the ability of future generations to meet their own needs”. Over the next half-century, it is very likely that climate change will make sustainable development more difficult, particularly as measured by their progress toward achieving Millennium Development Goals for the middle of the century. Climate change will erode nations’ capacities to achieve the Goals, calibrated in terms of reducing poverty and otherwise improving equity by 2050, particularly in Africa and parts of Asia (very high confidence) [20.7.1].
Even though there are cases where climate-related extreme events have severely interfered with economic development, it is very unlikely that climate change attributed to anthropogenic sources, per se, will be a significant extra impediment to most nations’ reaching their 2015 Millennium Development targets. Many other obstacles with more immediate impacts stand in the way [20.7.1].
Sustainable development can reduce vulnerability to climate change by encouraging adaptation, enhancing adaptive capacity and increasing resilience (very high confidence) [20.3.3]. On the other hand, it is very likely that climate change can slow the pace of progress toward sustainable development either directly through increased exposure to adverse impact or indirectly through erosion of the capacity to adapt. This point is clearly demonstrated in the sections of the sectoral and regional chapters of this Report that discuss implications for sustainable development [see Section 7 in Chapters 3 to 8, 20.3, 20.7]. At present, few plans for promoting sustainability have explicitly included either adapting to climate-change impacts, or promoting adaptive capacity [20.3].
Sustainable development can reduce vulnerability to climate change.
Efforts to cope with the impacts of climate change and attempts to promote sustainable development share common goals and determinants including: access to resources (including information and technology), equity in the distribution of resources, stocks of human and social capital, access to risk-sharing mechanisms and abilities of decision-support mechanisms to cope with uncertainty. Nonetheless, some development activities exacerbate climate-related vulnerabilities (very high confidence).
It is very likely that significant synergies can be exploited in bringing climate change to the development community, and critical development issues to the climate-change community [20.3.3, 20.8.2 and 20.8.3]. Effective communication in assessment, appraisal and action are likely to be important tools both in participatory assessment and governance as well as in identifying productive areas for shared learning initiatives [20.3.3, 20.8.2, 20.8.3]. Despite these synergies, few discussions about promoting sustainability have thus far explicitly included adapting to climate impacts, reducing hazard risks and/or promoting adaptive capacity [20.4, 20.5, 20.8.3].
Discussions about promoting development and improving environmental quality have seldom explicitly included adapting to climate impacts and/or promoting adaptive capacity [20.8.3]. Most of the scholars and practitioners of development who recognise that climate change is a significant issue at local, national, regional and/or global levels focus their attention almost exclusively on mitigation [20.4, 20.8.3].
Synergies between adaptation and mitigation measures will be effective through the middle of this century, but even a combination of aggressive mitigation and significant investment in adaptive capacity could be overwhelmed by the end of the century along a likely development scenario.
Tables TS.3 and TS.4 track major worldwide impacts for major sectors against temperature increases measured from the 1980 to 1999 period. With very high confidence, no temperature threshold associated with any subjective judgment of what might constitute “dangerous” climate change can be guaranteed to be avoided by anything but the most stringent of mitigation interventions.
As illustrated in Figure TS.19, it is likely that global mitigation efforts designed to cap effective greenhouse gas concentrations at, for example, 550 ppm would benefit developing countries significantly through the middle of this century, regardless of whether the climate sensitivity turns out to be high or low, and especially when combined with enhanced adaptation. Developed countries would also likely see significant benefits from an adaptation-mitigation intervention portfolio, especially for high climate sensitivities and in sectors and regions that are already showing signs of being vulnerable. By 2100, climate change will likely produce significant vulnerabilities across the globe even if aggressive mitigation were implemented in combination with significantly enhanced adaptive capacity [20.7.3].
Figure TS.19. Geographical distribution of vulnerability in 2050 with and without mitigation along an SRES A2 emissions scenario with a climate sensitivity of 5.5°C. Panel (a) portrays vulnerability with a static representation of current adaptive capacity. Panel (b) shows vulnerability with enhanced adaptive capacity worldwide. Panel (c) displays the geographical implications of mitigation designed to cap effective atmospheric concentrations of greenhouse gases at 550 ppm. Panel (d) offers a portrait of the combined complementary effects of mitigation to the same 550 ppmv concentration limit and enhanced adaptive capacity. [F20.6]