Until sometime around the mid-90s, climate change was called ‘global warming’. Global warming makes it sound as though nothing much changes, except things get a little warmer; if you live in a northern climate, it almost sounds nice. But the results are much more dramatic and unpredictable than that; for example, warmer air can hold more water, so all sorts of weather events (e.g. hurricanes) can be more devastating. In France they sometimes use the name ‘dérèglement climatique’ which conveys nicely the idea that many accepted rules of climate and weather are going awry, that we are moving into unknown territory.
The exact consequences of climate change will depend on the actions we take now and in the future. Scientists have developed 4 scenarios on a spectrum of action possibilities that they label RCP 2.6 (relatively optimistic), RCP 4.5, RCP 6.0 and RCP 8.5 (the most pessimistic, described as ‘the nightmare scenario’). These scenarios were developed in 2000 and refined in 2014, so it’s too early to reliably say which one is the most realistic, but various sources, including the Atlantic, state that we are most closely tracking RCP 8.5. It’s worth emphasizing this; we are most closely tracking the nightmare scenario.
One clear pattern in recent years is that countries have talked a better game than they are playing. The 2015 Paris Climate Agreement showed that countries were willing to make vague promises, but when you look for concrete plans – even for the medium term – things are disappointing. For example, the EU has been unable to set a common objective for carbon neutrality in 2050, China intends to build many new coal power plants, Germany is only proposing to stop generating electricity with coal in 2038 and China continues to use banned gases. Adding to this the US’s withdrawal from the Paris agreement and Brazil’s deforestation policy, there are reasons to be skeptical when it comes to future actions.
Perhaps we get a better view of what’s coming when we look at some of the accelerators for climate change; in particular the scale of the ice melt and permafrost thaw observed today are 50 and 70 years ahead of predictions.
For all those reasons, I think that the most pessimistic predictions – those based on RCP 8.5 – are the most likely. Of course, there’s plenty of opportunity for us to improve this (after all, I’m writing this document in the hope we do so) but, right just now, I don’t see any good reasons to be optimistic.
Here are some of the consequences of climate change…
Rising Sea Levels
Sea levels are rising for two reasons. First, the water in the oceans is getting warmer and thus expanding. Second, the ice cap is melting and putting more water in the seas. By 2100 it is likely that sea level will be around a meter higher (estimates vary a lot, Wikipedia gives a range of 0.3 to 2.4 meters).
30% of the world’s population lives in low lying areas near the sea and they would all be directly affected (they would not all be flooded but their day to day activities would change) by this rise – we’re talking about a lot of economic cost. Island nations – e.g. the Maldives – would lose their fresh water supply and be uninhabitable. 30% of Bangladesh would be flooded and 30 million people displaced. Low lying cities like Miami, Osaka, the Hague, Rio de Janeiro and Alexandria would all be directly threatened by such a rise. The UK’s National Oceanographic Centre report suggests sea level rise alone could cost the world $14 trillion dollars per year in 2100.
Not all of the carbon dioxide we are releasing into the atmosphere stays there; around 25% of it dissolves in the oceans. This CO2 absorption reduces the warming effect we are having on the planet but has the side-effect of making the oceans more acidic. We don’t know exactly how this will affect the marine ecosystem. We do know it dissolves shells as marine life are trying to develop them; corals, shellfish and molluscs struggle to develop properly. It also affects the development of plankton – the base of the food chain – with unpredictable and potentially disastrous results. Wikipedia provides a lot more details.
There is plenty of evidence that climate change increases the intensity and frequency of extreme weather phenomena like hurricanes, floods, storms and heatwaves; here is one such report. Higher ocean temperatures in the tropics favor the development of more intense hurricanes; we may need to introduce a new category 6 for hurricanes. The warmer atmosphere can also hold more water vapour; heavy rainfall events and floods are likely to be more extreme as a result.
All of these add up to more property damage; this is likely to affect us all through higher insurance premiums in the near future. It’s also likely more of us will choose to forego insurance or that insurance companies will stop offering cover for some events. Farmers are more vulnerable to weather events than most of us and seldom have comprehensive coverage; they are exposed to higher losses in the future.
Humans have a limited ability to survive extreme heat. At a wet bulb temperature of 35C – which would be around 46C with 50% humidity – a human is being cooked and death, even for a healthy person, will follow soon. Being indoors or in the shade, having lots of water to drink, resting and using cooling fans won’t change that. The only thing that will save you is air-conditioning or some other form of refrigeration.
We are on course to have this sort of temperature by 2100 occasionally during the summer in several places on Earth. One of these is the North China Plain; this contains huge cities – Beijing and Shanghai – and is vital to the country’s food production and economic interests. If you don’t have access to air conditioning in such areas, either you need to move elsewhere or you may die. There is more information in The Guardian.
If one country is affected more severely than its neighbor by climate change, then there is pressure to migrate. Climate change is definitely a driver for migration from Africa to Europe and from Central America to the USA. Climate change knows no borders, but migrants displaced by it certainly do; the USA and Europe are not keen at all to accept these migrants. There is a non-delicious irony that the very countries reluctant to host migrants generated the demand for migration when their pollution inflicted climate change on Africa and Central America.
Looking forward, countries that cover a lot of latitude (e.g. the USA, Canada, Chile and Argentina) may be able to delay the worst effects of climate change through internal migration towards the poles.
The hottest and poorest countries suffer most
If you are poor, then a relatively small economic problem (e.g. the price of flour increasing 10%) affects you much more than someone better off. An increase in average temperatures is more serious in a hot environment than a cool one. If you live in a poor country, it’s less able to handle problems brought on by climate change than a rich one; for example, it’s harder for a poor country to build a reservoir. If you farm for a living, you are more affected by climate change than someone working in an office. For all of those reasons and more, the consequences of climate change will be most acutely felt in the hottest, poorest countries; see reports in Grist and Mercy Corps. Africa did nothing to contribute to climate change but large tracts of the continent will be devastated by it.
One reason climate change will cause drought is via reduced precipitation. Rainfall patterns will change but predicting how different regions of the globe will be affected is harder than predicting temperature rise (see The Guardian). There’s a general belief that the wetter areas will get more rain (a warmer atmosphere can hold more water vapor) and that rain will often fall more intensely and cause flooding; and drier areas will get drier (see Nasa’s summary).
As temperatures increases, you need more water to grow the same crops; evaporation sucks more water out the soil. So climate change can cause drought by increasing the need for water.
Lastly, there are many places where snow and ice act as fresh-water reservoirs but are vulnerable to rising temperatures. The mighty rivers of Asia (e.g. the Indus, the Mekong, Ganges/Brahmaputra and Yangtze) provide drinking and irrigation water for around 2 billion people. All of these rivers start in the Himalaya and some – e.g. the Indus – flow through and permit agriculture in very dry regions. During droughts and the pre-monsoon period glacial meltwater maintains the flow in the rivers. These himalyan glaciers are melting fast and this will perturb the rivers’ flow. One projection shows increased flow in the Indus in the summer months over the next 50-100 years followed by greatly diminished flow when the glaciers are much smaller.
Fires seem to be getting bigger and bigger. Recent wildfires in Siberia have burnt an area the size of Holland and left an area the size of the EU under smoke; this is a triple disaster for air quality, CO2 release and soot darkening arctic ice (thus accelerating melting). ScienceNews reports on record fires through the Arctic and the resulting carbon emissions. There were devastating forest fires in California in summer 2018; the Atlantic reports that the increasing size of summer forest fires in the state are caused by climate change.
Up to now, climate change by itself hasn’t been a primary reason for an armed conflict but it has been cited as a contributory factor for the conflict in Darfur and in Syria. It’s depressingly likely that climate change will be the primary cause of major catastrophes – e.g. drought, famine and population collapse – and if a country believed that war could provide relief then it would become likely. A war over water rights from the Nile or the Indus? Or to permit migration of an entire population to a country less affected by climate change? This is speculation but it’s not incredible.
A Catastrophic Climatic Shift
Ocean currents and seasonal wind patterns control the weather throughout the world; as climate change continues it is not impossible that some of these patterns will change.
The monsoon in South Asia is a seasonal wind-reversal that brings much needed rain during the summer months to the whole area. If this phenomenon were to stop it would be catastrophic for the whole Indian subcontinent; 25% of the global population would be directly threatened. Of course, it’s unlikely to stop; but it could start happening later or it could be less strong (i.e. provide less rain) or it could become stronger (i.e.provide more rain, causing floods) or it could become more irregular. Any of these changes would have a huge impact on the Indian subcontinent.
The Gulf Stream is a current that pumps warm water from the Gulf of Mexico north-east across the Atlantic to Western Europe. This provides a relatively warm climate in Northwestern Europe; Glasgow is almost 1000 Km north of Quebec but has much milder winters. But the Gulf Stream probably has a more important effect; it cools the atmosphere by transferring heat to the oceans. The rate of flow of the Gulf Stream changes over time and we are currently in a period of lower flow. If the rate of flow were to keep falling or, much more catastrophically, it reversed then winters in Northwestern Europe would become much colder while the atmosphere as a whole gets hotter. As the Guardian reports, there’s a concern that ice-melt of Greenland and warmer seas could trigger such a change.
This is all, of course, speculation based on the idea of a tipping-point – at a certain point a small change suddenly has a big effect. But, as Wikipedia discusses, it’s a concern of climate scientists.