Effects of climate change

What are the effects of climate change?

A changing climate impacts crop growth and human health, while many people may need to leave their homes. It places certain species at an increased risk of extinction. The effects of climate change are real, and they are already happening.

The level of climate change we will see depends on how quickly we cut emissions of dangerous greenhouse gases. Even if we were to stop all emissions today, we would not prevent some changes. However, the sooner we cut emissions, the smaller the changes will be. 

Image showing some of the drivers of climate change and its impactsThis image illustrates some of the drivers of climate change and the impacts they could have on the climate system.

In a recent report, the Intergovernmental Panel on Climate Change (IPCC) showed the difference between1.5°C and 2°C of global warming. But unless we reduce emissions rapidly, the world is likely to exceed 2°C of warming. By the end of this century, warming could potentially reach 4°C, possibly more. 

Climate change will increase the risk of different problems around the world. Though developed countries produce most greenhouse gas emissions, developing countries are predicted to see most of the severe effects. With fewer resources to adapt to these changes, the impact on people in developing countries is expected to be higher. 

Effects of climate change on the planet

Average global temperatures have risen by more than 1°C since the 1850s. 2015, 2016, 2017 and 2018 were the hottest years ever recorded. The figures show us that the planet has been warming since the industrial revolution. 

A graph showing the global average temperature change from 1850 to 2018, compared to the 1961-1990 average. The plot continues to rise since the 1960s.

This plot shows the global temperature change from 1850 to 2018, compared to the 1961-1990 average temperature.

A warming planet leads to many other changes in our climate. As the planet warms, heatwaves become more likely. Over the past few years, heatwaves have been the deadliest global weather hazard.

Oceans absorb 90% of the extra heat generated by human influence. However, when water heats up, it expands to take up more volume. So, when oceans heat up, they expand too, causing the sea level to rise. We also have extra water flowing into the ocean from melting ice sheets and glaciers. Between 1902 and 2015, the global average sea level has risen by 16 centimetres.

Some parts of the planet, such as the north and south pole, warm more quickly than other places. At the poles, glaciers and ice sheets reflect energy from the sun into space. So, when there is less ice, less energy from the sun is reflected away. The area then heats even more quickly, causing even more ice to melt. 

The ice in the Arctic is melting fast. It is already 65% thinner than it was in 1975, and if we do not reduce emissions soon, we could see ice-free summers in the Arctic by the middle of this century. 

When ice sheets and glaciers melt, freshwater flows into the sea. As well as making the sea level rise, freshwater also reduces the salinity (saltiness) of the water, which can slow or change ocean currents.

Oceans also absorb around 25% of the carbon dioxide that humans release into the air. The oceans then become less alkaline, a process called 'ocean acidification'. Ocean acidification is bad because it can have negative effects on marine organisms, like coral and plankton, which are an important part of the food chain.

Changes to the UK climate and weather events

Changes in intensity or frequency so far Is this linked to climate change? What is expected in the future?
UK warm spells Increase Yes Increase
UK cold spells Decrease Yes Decrease
UK heavy rain Increase Inconclusive Increase
UK dry spells No trend detected Inconclusive Increase (summer)
UK wind storms No trend detected Inconclusive Inconclusive

Changes to the global climate and weather events

Changes in intensity or frequency so far Is this linked to climate change? What is expected in the future?
Global heatwaves Increase Yes Increase
Global cold events Decrease Yes Decrease
Global heavy rain Increase Yes Increase
Global drought Increase* Yes* Increase
Global tropical storms No trend detected Inconclusive Increase and decrease**

* Marvel et al 2019 provides new evidence drought increased in some regions during specific periods since 1900 (with aerosols possibly masking the trend when it is not detectable), and that this is connected to climate change.

** Possible decrease in frequency and possible increase in intensity (and associated rainfall). 

Warmer air can hold more water, so rainfall is increasing on average across the world. In some places, rainfall is becoming more intense as well. However, some areas receive less rain because of changes in wind patterns.

Effects of climate change on humans

We are already experiencing the effects of a changing climate. Rising sea levels cause problems for people around the world. Nearly 4 in 10 people (39%) live within 100 kilometres from a shoreline and are at risk of flooding if sea levels continue to rise. 600 million of these people live in a 'low-level coastal zone', and 200 million on a coastal flood plain.

Even if we cut emissions, sea levels will continue to rise until the year 2100. But, if we reduce emissions enough, we can slow the rate of increase. Many people will have to leave their homes, but the number will vary depending on how we act, by reducing global emissions and improving flood defences.

Floods can also happen when heavy rainfall overwhelms drainage systems or bursts river banks. In heavily concreted urban areas and cities, the effect is more severe because the water cannot sink directly into the soil. Flooding causes severe damage to buildings and transportation, which can be very costly and hard to recover. 

As our climate warms and rainfall patterns change, it may be harder to grow enough food in some areas. The climate will change which crops can grow in different regions. Some places may be able to grow new crops, but many places will experience reduced crop production, especially in hotter countries. 

Colder countries are likely to see higher yields because there will be a longer growing season and higher carbon dioxide concentrations. However, these effects may not last if warming continues in the longer term. More extreme weather events could also disrupt access to food, impacting transport from farms to shops, which can affect vulnerable people.

As you can see, climate change has a lot of effects, and they impact people around the world in different ways. The level of impact depends on the climate of the area and the wealth of the country. Climate change effects are 'stress multipliers', which means that they often make existing problems more severe. 

Let's look at heatwaves, for example. We expect most regions will experience more intense heatwaves. In countries that are already hot, the human heat stress limits will be exceeded more often, which is dangerous. 

As another example, an increase in flooding is another danger. Countries that flood regularly, such as Bangladesh, are expected to see even more regular floods, putting more communities at risk.

This graph, from Munich RE's Topics Geo Natural Catastrophes report, shows events causing loss are becoming more frequent.

If our climate continues to change, many parts of the world will become more challenging places to live. People may have to leave their homes. Climate is just one of many factors that influences human migration, but it will play an increasing role in the future. 

Effects of climate change in the UK

Climate change is causing warming across the UK. All of the UK's ten warmest years on record have occurred since 2002. Heatwaves, like that of summer 2018, are now 30 times more likely to happen due to climate change.

UK winters are projected to become warmer and wetter on average, although cold or dry winters will still occur sometimes. Summers are projected to become hotter and are more likely to be drier, although wetter summers are also possible. By 2050, heatwaves like that seen in 2019 are expected to happen every other year. 

Even if we do reduce greenhouse gas emissions, sea levels around the UK will keep rising beyond 2100. Parts of the UK will be in danger of flooding, with low lying and coastal cities at particular risk. 

Heavy rainfall is also more likely. Since 1998, the UK has seen seven of the ten wettest years on record. The winter storms in 2015 were at least 40% more likely because of climate change.

Farming in the UK will be affected by climate change, too. Hotter weather and higher levels of CO2 may make growing some crops easier, or even allow us to produce new ones. However, with more droughts expected, water may not be as easy to access, making it harder for farmers to plan the growing season.

Floods, storms, and extreme heat can cause damage to buildings, disrupt transport, and affect health. Buildings and infrastructure need to be adapted to cope with the new conditions. Businesses will have to plan around a changing climate. To help the UK understand what climate change means for the nation, the UK Climate Change Risk Assessment is published every 5 years. More details of the future conditions expected for the UK are available in the UK Climate Projections (UKCP18)