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Adaptation To A Changing Climate

Climate change is expected to cause more frequent and severe hazards. In partnership with Statkraft, Shell, TCS and Xyntéo, we have identified some of the most prominent climate hazards. A more focused analysis, based in part on the latest findings from the IPCC Fifth Assessment Report, is summarised in the report “Climate science – a perspective for business leaders“.

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Rising Sea Waves on cliffs

Rising sea

Rising sea level is one of the greatest threats to low-lying islands and coasts. This century it could go up by more than a metre. If ice sheets collapse, the sea could rise by several metres over a few centuries.


Today the sea is rising at more than 3 millimetres per year, as warming water expands and as glaciers melt. Predictions for 2100 vary, but the rise could be up to about 1.5 metres if emissions stay high.   This could combine with growing storm surges, [Flood] to threaten coastal settlements with flooding and fresh water pollution. By mid-century millions of people may be displaced. According to a World Bank/OECD study, global economic losses could reach a trillion dollars per year by 2050 if defences are not improved.

The Greenland and West Antarctic ice sheets may reach tipping points where collapse over a few centuries becomes almost inevitable. Greenland holds enough to raise global sea level 7 metres; the West Antarctic 3 to 5 metres. To predict future rises, scientists can add up the thermal expansion of the sea and the melting of land ice. In the IPCC’s latest report, this approach is used to project 0.53 to 0.97 metres rise this century for high emissions (RCP8.5), and 0.28 to 0.60 metres for low emissions (RCP2.6). But this “process-based” method may not include the full effect of glaciers draining ice from Greenland and Antarctica. Alternative “semi-empirical” models, based on past observations, produce higher projections – from about 0.7 to 1.65 metres for RCP 8.5.

Sea level will be uneven because of changes in ocean currents and the shifting masses of ice. Among the fastest-rising sea levels will be along the US East Coast and near the equator.   In Southeast Asia, tens of millions could be displaced by 2100. Some low-lying island states may be obliterated – such as Tuvalu, which lies in a region of rapid sea-level rise.   Among industrial nations, many large coastal cities are at risk. The World Bank study names Guangzhou, Miami and New York as the three cities with the highest projected economic losses.

Smoke cloud

Storms

Hurricanes and typhoons are expected to become more intense, with higher wind speeds and precipitation rates. There is already evidence for more intense hurricanes in the North Atlantic.


Tropical cyclones (hurricanes and typhoons) are driven by the energy of water evaporating from the sea. A warmer sea means more evaporation and more energy available to power a storm. So global warming is expected to increase the intensity of some cyclones.   The overall number of cyclones is not expected to increase, but it is the most extreme storms that present by far the greatest hazard. In 2013, Super Typhoon Haiyan was one of the most powerful cyclones ever to make landfall. It killed more than 6000 people in the Philippines.

Historical records are patchy, and the evidence for increasing cyclone intensity is limited in most areas. The North Atlantic is an exception; there it is virtually certain that the frequency and intensity of the strongest tropical cyclones has increased since the 1970s.   Globally, climate models bear out the conclusions of basic physics, and project that the strongest storms will probably get stronger in future. The IPCC predict “a likely increase in both global mean tropical cyclone maximum wind speed and precipitation rates” over the coming century.

Climate change may also change the geographical range of storms, potentially bringing more hurricanes to the northeast coast of the US and to Europe.

flooded city

Floods

Warming will boost the potential for extreme rainfall, simply because warmer air can hold more moisture. Downpours won’t increase everywhere, but a majority of the planet is expected to face more and heavier floods.


Wet climates are likely to get wetter this century. Uncertainty remains, but models project a likely increase in extreme downpours where floods are already common: most severely in Southeast Asia, India, East Africa and around the northern Andes. Meanwhile many drier regions are likely to see less flooding than before – for example southern and Eastern Europe, and many parts of central North America. Among the most common risks are damage to property, crops and infrastructure, such as electricity distribution. Probably the deadliest recorded floods hit China in 1931, during months of heavy snow and rainfall. Some sources put the death toll as high as four million. 

While flooding is expected to increase globally, regional projections are made with lower confidence. Precipitation is not as easy to predict as temperature. It depends strongly on complex weather phenomena - especially the behaviour clouds, which is difficult to model explicitly. Rain only leads to flooding when it overwhelms a river system, which depends on local factors including soil and land use. The concrete and asphalt of cities can prevent water from soaking away, for example. Meanwhile coastal flooding is almost certain to increase as sea levels rise. Coastal floods may be boosted further by growing storm surges from more intense storms.

Expreme wave

Extreme waves

Extreme waves seem to be growing in size, and are expected to loom higher still as the climate changes. The largest waves threaten ships, offshore platforms and wind turbines.


Wind makes waves. So if weather gets stormier, extreme wave height is liable to increase. Evidence comes from visual observations by ships’ officers, and from buoys, marine radar and satellites. Despite some discrepancies between these sources, they all show increasing extreme wave height in the North Atlantic, the Southern Ocean and the Northern Pacific.   Ships are most obviously vulnerable. The greatest risk posed to large ships is sagging: mechanical failure of the deck and hull when wave crests lift bow and stern. Offshore platforms can be damaged by waves higher than the main deck. Growing extreme waves could also present a challenge to ports, sea defenses and other coastal infrastructure. 

Wave height depends not only on local wind strength, but also wind direction and steadiness, the position of land masses, and the arrival of sea swells from distant ocean basins. So changes in wave behaviour will depend strongly on location. Climate models suggest that wave height will continue to rise in many places. The North Atlantic, for example, is one of the busiest regions for shipping and already has some of the world’s largest deep-ocean waves. Under once-in-20-year storm conditions, typical wave heights there are around 16 metres. By the end of the century, that could rise by roughly a metre according to some models - although the numerical uncertainty is large. Climate change may also increase the number of dangerous “rogue waves”, which can be more than double the typical wave height.   One of the most secure predictions is for the Arctic Ocean, where melting sea ice [Ice and Snow] will mean more open water and almost certainly larger waves.

Sun

Heatwaves

It is no surprise that in a warmer world, we will almost certainly see more heatwaves. Extreme heat can kill directly, destroy crops, damage roads and other infrastructure, and spark wildfires.


Models project that heatwaves are very likely to become more frequent and last longer. Records show evidence that this is already happening.   Deaths in a heatwave come mainly from respiratory and cardiovascular conditions. When a record-breaking heatwave hit Europe 2003, tens of thousands died.   A heatwave usually means very high temperatures lasting for several days, but many of the same risks arise even if high temperature is too brief to be labelled a heatwave. Among other forms of infrastructure, power transformers are vulnerable to high temperatures, especially where use of air conditioning means electricity demand increases.

As global mean temperature rises, the statistical distribution of temperatures will shift, so that heatwaves once considered extreme and rare will become much more commonplace.   There is also evidence that the variance in temperature is increasing. Feedback mechanisms in the climate may be behind this. For example, plants that normally cool the air are less able to do so under drought conditions.

Along with other forms of extreme weather, heatwaves may become more prolonged as the polar jetstreams slow down and meander more lazily, which is liable to slow down or halt the movement of weather systems.

Ice and Snow

Ice & snow

Arctic sea ice is shrinking fast, while glaciers retreat and permafrost thaws. The global thaw presents a range of risks to nature and human society, and a few opportunities too.


As air and oceans warm, ice melts. In the Arctic, more than 60% of summertime sea ice volume has been lost. Later this century, that is likely to reach 100%. The loss will have a powerful effect on ocean ecosystems and fisheries. Thawing permafrost can undermine roads and other infrastructure, while ice roads disappear. Meltwater from glaciers is raising sea level. The loss of mountain glaciers will hit water supply and food production in areas such as Peru and the Indus river basin. Melting ice will cause mountain landslides. The global thaw also brings some positive effects: new Arctic shipping routes and new opportunities for hydropower. 

The thaw is driven both by rising temperatures and by soot from burning coal, wood and diesel. This “black carbon” can settle on snow and ice, absorbing solar heat. As well as presenting several hazards, melting ice leads to dangerous climate feedbacks. Snow and ice reflect solar heat, so as they disappear the Earth warms up. An influx of fresh water from melting glaciers may interfere with ocean circulation. And thawing permafrost could release huge amounts of stored carbon into the atmosphere, accelerating global warming in what would be an effectively irreversible climate tipping point. The ice sheets of Greenland and Antarctica may see another kind of tipping point, beyond which they inevitably collapse, over a few centuries, adding several metres to sea level.

Wildfire

Wildfires

With warmer air and longer droughts to dry out vegetation, conditions are likely to generate more wildfire. Signs are that this is already happening in some regions, with increased risk to homes and businesses.


 As many dry areas of the world are expected to become even drier due to climate change, wildfires are likely to proliferate. Already there is evidence of spreading fire in some regions. In the western US, fires have become larges and longer-lasting since the 1970s, even where land use has not changed. This trend is put down to higher temperatures and earlier snowmelt.   On 7 February 2009, Australia saw the most destructive bushfires in its history. After a long drought, in heat of 45°C and fanned by high winds, hundreds of bushfires blazed across the state of Victoria, killing 173 people. 

Semi-arid regions are most at risk. Climate models project a high probability of increased wildfires in the western US, central Asia and Australia, the Sahel and southern Africa, among others. However, some regions are expected to see fewer fires as average rainfall increases. This reduction is likely in parts of tropical Africa and Southeast Asia. These predictions of regional change are not certain because the causes of wildfire are complex, including the desiccating effects of global warming and also changes in vegetation, which determines the fire’s fuel supply. Changing land use can increase or decrease the hazard; while increases in biomass owing to climate change are liable to prompt more frequent fires. In turn, the increasing geographical range of wildfires will alter some ecosystems, for example replacing forests with grassland.

Drought

Droughts

Causing famine and spreading disease, drought is a grave hazard. Droughts are expected to become longer and more intense in many areas of the world as temperatures rise and rainfall patterns change.


Dry lands today are likely to get even drier over the coming decades, according to climate models. Longer and more intense droughts are already hitting some regions, including southern Europe and West Africa. An obvious consequence is food shortage as crops die. Drought can also help spread disease, erode topsoil, and lead to wildfires and dust storms. Industry can be hit as water supplies dwindle. Hydroelectric power depends on river flow, and many thermal power plants use river water for cooling. 

Drought can be caused by lower rainfall and by higher temperatures, which dry out the soil. In turn, drought can prevent plants from cooling the air, so temperatures rise even further. Drought is relatively complex to predict, and future changes will depend on the location, but models agree that much of the world will become increasingly arid. That includes most of the Americas, Australia, Southeast Asia, Africa, southern Europe and the Middle East. According to one study, people living in these regions may see a switch to persistent severe droughts in the next 20 to 50 years.

Ocean Acidification

Ocean Acidification

Sea water is absorbing carbon dioxide from the atmosphere, making it more acidic. Many organisms including corals and crustaceans are at risk, along with the fish and other creatures that feed on them.


 The acidity of the ocean has already increased by 30%. This will continue to rise for some decades even if emissions are cut.   Many ocean organisms build shells or skeletons from calcium carbonate, which becomes difficult and then impossible as acidity increases. Acidification could undermine whole ecosystems, as larger ocean creatures feed on vulnerable organisms including plankton, corals and molluscs. Fisheries and tourism will be hit. The effect will be greatest in cold water, where CO2 is more soluble. The Southern and Arctic oceans may be unable to support some shell-building organisms if atmospheric CO2 reaches 450 parts per million – a level likely before mid-century. 

The chemistry of the oceans will change radically unless CO2 emissions are cut drastically. In a mid-range emissions scenario, the ocean’s acidity will have more than doubled by 2100 (with a decrease in pH value of more than 0.3). Seawater would then be more acidic than it has been for at least 20 million years. Ancient episodes of acidification have been linked to large-scale extinctions of marine life.   As well as interfering with shell and skeleton building, acidity may damage the health of fish. Acidification also affects the acoustic properties of water. Higher acidity means that sound travels further, threatening marine mammals that are already vulnerable to noise from human and natural sources. While many organisms and ecosystems are vulnerable, one exception may be sea grasses, which could benefit from higher levels of CO2.

Landslide

Landslides

When heavy rain soaks the ground it adds weight that can trigger a landslide. A warmer, wetter world in the future will probably mean more landslides. Along with other mass motions including mudslides and lahars, landslides are often deadly and destructive.


Rainfall is the most common trigger for landslides. Because heavy precipitation is expected to become more common, landslides probably will too. Rising temperatures will also destabilise some mountain slopes that are now frozen.   Some forms of landslide are lubricated by water and flow over long distances. That includes mudslides, lahars and debris flows. The destruction can be vast. In Venezuela in 1999, torrential rain caused mudslides that killed 30,000 people and left 400,000 homeless. Warming may also trigger landslides on the sea floor. Changes in pressure and temperature, and the movement of land masses as melting lifts the weight of ice, could destabilise sediment slopes. Submarine landslides can cause tsunamis. 

Landslide hazard is very site-specific, depending on surface topography and underlying geology, as well as vegetation cover. Generally, risks are greatest on mountainous areas. Scientists can assess the stability of a slope, and what level of rainfall might pose elevated risk; but it is difficult to quantify the probability of collapse, and to predict the most likely size and type of landslide. There is some evidence that landslides are already becoming more frequent. It remains uncertain because of changes in population, communications and reporting. Also, the role of climate change is obscured by other changing factors including deforestation, which also increases landslide hazard. Most human structures are vulnerable to landslides, including roads, bridges and powerlines. Real estate prices and tourism may be hit in some areas if landslides become more frequent.