Climate Impact
A 4 °C rise in global temperature by 2100 is the expected result if we continue to ignore the problem of escalating harmful emissions like CO2. The rise will not be perfectly uniform across the world. For instance, the oceans heat up slower than the land and in high altitudes such as in the Arctic the temperature rises will be higher.
It is also predicted that the hottest days will be a lot hotter and this has inevitable implication on health (heat stress, water scarcity related harm), agriculture and commercial productivity. Although there are regional differences around the world in what to expect with temperature rise the one common element that all countries share is that there will be significant changes that will impact on the environment and these will be irreversible changes.
Too hot for comfort
A heatwave in Europe in 2003 was responsible for around 35,000 deaths. In an unmitigated future climate, the frequency of events like this is likely to increase. The approximate trigger thresholds at present for various cities are:
| Boston | 26 °C |
| Budapest | 28 °C |
| Dallas | 34 °C |
| Lisbon | 28 °C |
| London | 24 °C |
| Sydney | 26 °C |
These temperatures are all regularly exceeded during present day summertime.
This means that heat-related deaths affect approximately 1–6 people per 100,000 per summer. In the scenario of a global mean temperature rise of 4 °C, it is foreseeable that heat-related mortality may increase considerably, even taking into account possible acclimatisation and adaptation.
Agriculture, food production and water
Agricultural yields are expected to decrease for all major cereal crops in all major regions of production. Land suitability for cultivation will be reduced. Climate change will reduce, for instance, soybean yield and production — also a major crop that produces protein and oil.
A food shortage through climate change could result in tens to hundreds of millions of additional people at risk from hunger. The Sub-Saharan Africa is particularly vulnerable in this respect as are some parts of south Asia and Central America. For the global population at 2050 the amount of malnourished children could total around 24 million.
With the 4 °C rise the availability of water would be a serious problem. By 2080 the population will rise, and even without climate change, just over 3 billion people, out of a global population of 7.5 billion, could be living in areas with limited per capita water availability (less than 1000 m3/person/year).
By reducing river run-off, climate change could mean that significantly less water was available to approximately 1 billion of these people. Communities relying on glacier melt-water will also come under threat.
Escalating emissions
The 20th Century rise in CO2 concentration was only 40–50% of the actual rate of emissions. The remainder was absorbed by the world's ecosystems and oceans. This process will be damaged by climate change and the impact of emissions on atmospheric concentrations could be greater in the future. The proportion of CO2 emissions remaining in the atmosphere could rise to 70%.
A sea change
A rise of global temperatures will lead to sea-level rise. Low-lying coastal areas will become prone to flooding and more land will become unusable. Dense populations and infrastructure near water will be under increased threat. At the beginning of the 21st Century, an estimated 600 million people live no more than 10 metres above present sea level.
South and East Asia have high populations living in low-lying deltas and small islands are vulnerable to sea-level rise.
