What do climate tipping points mean for the UK?

Risk assessment

Understanding the impact of tipping points is an important element of climate change risk assessment, and a Met Office report was produced on impacts to the UK for input to the Third Climate Change Risk Assessment (CCRA3) Technical Report. In this report, three classes of Earth system instabilities were considered – those that could affect the UK directly through changes in our regional weather and climate; those involving changes in land ice, affecting sea level rise impacts in the UK and worldwide; and those related to feedbacks involving carbon or other biogeochemical cycles (e.g., the water cycle). Here we focus on some of the key instabilities which are likely to have the greatest impacts in the UK if tipping points occur.

Atlantic Meridional Overturning Circulation (AMOC)

The AMOC is a system of ocean currents which redistributes heat and carbon throughout the climate system and is responsible for a mild climate in the UK. Some studies suggest that the AMOC could have a tipping point, with evidence that the circulation has collapsed into a state of reduced flow in the distant past, from climate records taken from geological and biological materials such as sediment and tree rings. Although it is believed unlikely that the AMOC will collapse before 2100, there is scientific uncertainty around this, and a collapse could cause significant and widespread impacts across the UK, Europe and beyond. UK and European impacts are explored in the latest Marine Climate Change Impacts Partnership Ocean Circulation report.  

Changes in temperature, wind and rainfall patterns as well as increases in storm surges would have wide implications for the UK such as impacts on agriculture, marine industries and renewable energy production. High wind speeds can cause damage to wind turbines, whilst colder temperatures in winter could have human health impacts and increase energy demand.

Sea level rise 

There are two major contributors to sea level rise globally – thermal expansion of water as oceans warm, and an increase in the amount of water in the ocean as ice sheets and glaciers shrink. Of these, increasing water mass accounts for two thirds of sea level rise totals, and a large component of this is due to the accelerating loss of major ice sheets in Greenland and Antarctica. The Met Office climate dashboard provides a comprehensive way to stay up to date on the current state of the climate by providing data based on observations of key global climate indicators including sea level rise. We will also look in more detail at sea level rise tipping points later this month. 

Of most concern for the UK in terms of sea level rise is the risk of abrupt change to the West Antarctic Ice Sheet. Current climate projections indicate up to ~1m rise in sea level around the UK by 2100. Under certain circumstances, melting of the ice sheet can rapidly accelerate, and reaching these tipping points could cause ice sheet collapse. This irreversible shrinking of the ice sheet would commit the UK and the world to a much faster rate of sea level rise – up to 2m in the UK this century and even higher sea level rise beyond 2100.These scenarios are included in what are known as H++ scenarios – low likelihood but plausible extreme possibilities for future sea level rise. 

Rising sea levels can cause a range of impacts; changing the shape of our coastline and beaches, and threatening infrastructure and the homes of people who live in coastal communities. Rising sea levels can also threaten the survival of already fragile wildlife habitats.  

North Atlantic Jet Stream

The North Atlantic jet stream is closely linked to UK weather patterns and there is concern that this could weaken or change position due to a reduction of Arctic sea ice. The position and strength of the jet stream can alter the frequency and/or magnitude of high‐impact or extreme weather events in the UK. There is, however, scientific uncertainty about the likelihood of changes to the jet stream and the exact nature of the impacts which would be experienced. As impacts could have notable implications for the UK’s weather and climate, research in this area is important to fill those knowledge gaps.

Indirect impacts

Other tipping points may also have indirect impacts for the UK weather and climate. For example, a significant decrease in size of forests such as the Amazon rainforest would reduce the efficiency of terrestrial carbon sinks – which absorb more carbon from the atmosphere than they release – leading to increased atmospheric concentrations and accelerated global warming. This is turn could cause a cascade of further tipping points as well as other impacts associated with a warming climate.  

Impacts of other tipping points around the world could also impact the UK indirectly due to socio-economic instability generated by climate changes elsewhere in the world.

Taking action

Mitigating against a changing climate by reducing greenhouse gas emissions is critical to limiting warming which would help us avoid the worst impacts of climate change, including those which could be caused by reaching tipping points. Some of these impacts will be irreversible and if they happen before emissions are reduced, we will be committed to that impact in the future. 

We also need to adapt to the climate changes we are already seeing and the changes that are expected in the coming decades to make sure we avoid the worst impacts. While crossing major climate tipping points may be unlikely, it is important to understand the wider impacts and risks if they were crossed and to develop early warning indicators that would allow society time to respond. 

Action is required across all levels of society – to find out more about how you can make a difference, take a look at our Get Climate Ready webpages. 

Follow the #GetClimateReady hashtag on X (formerly Twitter) to learn more about tipping points this month.