What are the effects of Climate Change so far?
Climate change is not a future problem, it is something that is already underway, and is set to get worse as long as emissions continue to rise. In February 2022 the Intergovernmental Panel on Climate Change (IPCC) produced Climate Change 2022: Impacts, Adaptation and Vulnerability [1] as part of its 6th assessment report cycle. This document reported on the global scientific consensus on the effects of climate change to date. The highlights of this report, and of other scientific reports, were as follows:
Global Temperatures
The report found that human emissions of greenhouse gases had already warmed the planet by an average of 1.1°C since the beginning of the industrial era, with the majority of the warming occurring since 1975 at a rate of roughly 0.15 to 0.20°C per decade. Unless immediate steps are taken to reduce greenhouse gases the world is likely to exceed 2°C of warming in the coming decades, and by the end of the 21st century warming could reach 4°C and possibly more [2]. The level of global warming which the IPCC considers safe is below 1.5°C. The further the world goes beyond 1.5°C of warming, the more severe the consequences are predicted to be, with the added risk of the natural release of additional greenhouse gases through feedback factors.
Although a 1.1°C rise in temperature does not sound like a lot, when you are dealing with a rise in the average temperature for the entire planet, this represents a huge amount of energy. A five degree drop in average global temperature for example would be enough to trigger a new ice age and cover northern Europe once again in a towering mass of ice. With a global rise in the average temperatures then the danger is not of a new ice age but of a global 'heat age' with equally devastating results
Ice Sheets
Global warming does not affect all parts of the planet equally. Most of the warming is concentrated in the polar regions, where there are vast quantities of fresh water locked up in the great ice sheets of the Arctic, Greenland, and the Antarctic. Although the global average temperature has increased by 1.1°C since the industrial era, the average temperature at the poles has increased by several times this value.
For example, the image below shows global temperature anomalies in 2022 [3].These are not absolute temperatures, but changes from the norm for each area. The redder the area the higher the average temperature has been from the norm. The graph shows that the warming at the poles is far more than at the equator. Other studies [4] show that the Arctic has warmed four times more than the rest of the planet since 1979, by some 3°C.
As a result climate change is affecting the polar regions far more than other regions. The ice in the Arctic for example is already a terrifying 65% thinner than it was in 1975, and in recent years the ice sheet has become smaller than at any time in the last 1,000 years. The Arctic has lost enough sea ice to fill the area of Texas, California, Colorado and New York combined. This is causing the North Atlantic drift, often known as the gulf stream, to slow down, and is at risk of crossing a threshold after which it collapses altogether [3b]. This will have disastrous consequences for the UK and northern Europe, as this huge current of warm water warms the air as it drifts north and allows the temperature of the UK and northern Europe to stay mild. Without it, we would experience temperatures that are on average 3 to 5°C lower, leading to much harsher wintry conditions similar to Iceland
Sea Level Rise
On the other hand the Greenland ice sheet has also been shrinking every year for the last 25 years. According to the IPCC the Greenland ice sheet is melting at twice the rate of Antarctica and raising sea levels by three quarters of a millimetre per year. Even if the world stopped emitting greenhouse gases today, the amount already locked into the atmosphere will continue to melt the Greenland ice sheet and cause a global sea level rise of one foot by 2100, threatening the world's coastal areas.
Since 1880 the warming of the world's oceans and the melting of the ice sheets have caused a global sea level rise of 7 to 8 inches (21 to 24 cm), and the rate of sea level rise is speeding up. Predicting how this is set to increase in future decades however is complex, as it depends on factors such as how much greenhouse gas humanity continues to pour into the atmosphere and also on the melting patterns of the ice sheets in places like Greenland and the Antarctic. The graph below shows the possible scenarios, where the high scenario represents continued high rates of greenhouse gas emissions and a rapid ice sheet collapse once a tipping point is reached. In this scenario, global sea level rises by 7 feet by 2100, totally changing the map of the globe and causing massive devastation.
Extreme Weather & Other Climate Related Events
The IPCC report lists a large number of events that human induced climate change is already causing. These include:
Widespread, pervasive impacts to ecosystems, people, settlements, and infrastructure have resulted from increases in the frequency and intensity of heat waves on land and in the ocean, as well as heavier rain and snow, drought and fire.
The bleaching and dying of tropical coral reefs.
An increase in human deaths and in the deaths of trees from heat waves.
A greater severity and strength of tropical cyclones.
Increases in the frequency and intensity of extreme weather events have reduced food and water security, hindering efforts to meet Sustainable Development Goals
Roughly half of the world’s population currently experience severe water scarcity for at least some part of the year due to climatic and non-climatic drivers.
Hot extremes including heatwaves have intensified in cities, where they have also aggravated air pollution events and limited functioning of key infrastructure.
Climate change is contributing to humanitarian crises where climate hazards interact with other vulnerabilities, and climate and weather extremes are increasingly driving displacement in all regions.
Approximately 3.3 to 3.6 billion people live in contexts that are highly vulnerable to climate change.
Ocean acidification
The world's oceans absorb around 30% of the carbon dioxide emitted by human activity, and this means that the higher the levels of CO2 in the atmosphere go, the higher the levels in the world's oceans go too. As a result the world's oceans have absorbed a huge amount of CO2 since 1800, and this has changed the pH of the ocean, causing it to become more acidic. This trend is set to continue as human activity continues to drive up CO2 levels in the atmosphere, and as a result current levels of acidity in the ocean are on a path to reach a higher level than at any other time in the last 300 million years.
A large number of the organisms that live in the ocean rely upon the formation of a shell, such as oysters, clams, sea urchins, shallow water corals, deep sea corals, and calcareous plankton. The higher acidity of the ocean affects the ability of these organisms to form shells, and in some cases even dissolves them, threatening the stability of the entire marine food chain and the marine fisheries that rely on them. Around the world some 3 billion people rely on marine food for a significant proportion of their dietary needs.
Due to the seriousness of ocean acidification on the biodiversity of the ocean and the world's food supply, ocean acidification has been called the 'evil twin' of global warming. The deadly trio of increased temperatures, oxygen loss and acidification are placing severe pressure on the marine ecosystem.
Biodiversity Loss
The IPCC report a large number of effects that climate change has already had on biodiversity, such as:
Substantial damages, and increasingly irreversible losses, in terrestrial, freshwater and coastal and open ocean marine ecosystems.
Widespread deterioration of ecosystem structure and function, resilience and natural adaptive capacity, as well as shifts in seasonal timing.
Approximately half of the species assessed globally have shifted polewards or, on land, to higher elevations.
Hundreds of local losses of species have been driven by increases in the magnitude of heat extremes, as well as mass mortality events on land and in the ocean and loss of kelp forests.
Some losses are already irreversible, such as the first species extinctions driven by climate change. Other impacts are approaching irreversibility such as the impacts of hydrological changes resulting from the retreat of glaciers, or the changes in some mountain and Arctic ecosystems driven by permafrost thaw.
A high proportion of species is vulnerable to climate change. Human and ecosystem vulnerability are interdependent.
The report says that the extent and magnitude of climate change impacts are larger than estimated in previous assessments, and that overall, projected climate change, combined with non-climatic drivers, will cause loss and degradation of much of the world’s forests, coral reefs and low-lying coastal wetlands.
[1] https://www.ipcc.ch/report/sixth-assessment-report-working-group-ii/
[2] https://www.metoffice.gov.uk/weather/climate-change/effects-of-climate-change
[3] https://earthobservatory.nasa.gov/world-of-change/global-temperatures
[3b] https://phys.org/news/2022-06-huge-atlantic-ocean-current-downif.html