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Reducing uncertainties

Much of NERC climate change research is aimed at reducing uncertainties.

What makes climate change science uncertain?

Future emissions

Populations and economies are growing rapidly in developing countries, and their total greenhouse gas emissions could surpass those of developed countries over the next generation or so.

The carbon cycle

Carbon moves around the Earth's system in vast quantities - from the atmosphere to the soils and oceans, sometimes it is locked away deep underground for millions of years and recently, since the industrial revolution large amounts have been released into the atmosphere. The oceans absorb about half the carbon dioxide humans release into the atmosphere. Changes in climate will affect how carbon (and hence carbon dioxide) is stored, released and transported around the globe. We need to know more about carbon movement, for example, warmer conditions might encourage faster plant growth, locking away carbon. But warmer soils could also mean the carbon plants fix in photosynthesis rots down faster, releasing carbon back to the atmosphere.

Aerosols

Global warming may proceed more quickly and be more severe than previously predicted. As industry and transport become more efficient they are emitting less pollutants, improving air quality. Airborne particle pollution, or aerosols, reflects some heat from the sun back out to space. Cutting aerosol pollution reduces this reflection, allowing more of the sun's energy to reach the Earth's surface and raising temperatures.

Aerosols from natural sources, such as volcanoes, wildfires, dust, sea-salt spray and desert sands also have a cooling effect on the planet so understanding their impact on the climate is also important.

Also see the section "What is global dimming?"

Clouds

Clouds can reflect incoming solar radiation back into space, keeping heat out. But they can also prevent heat escaping from the Earth's surface. Their effects depend on their height, temperature and properties, all of which vary in time and from place to place. Modelling and observing techniques, from the Earth's surface and space, have greatly improved in recent years, but clouds remain one of the biggest uncertainties in climate change research.

Water vapour

A warmer atmosphere can hold more moisture, which itself acts as a greenhouse gas, generating further warming. Without this effect, the predicted warming would be halved. Scientists are still uncertain how to represent water vapour in climate models.

Ice and snow

Melting sea-ice and reduced snow cover in polar regions mean that the planet's surface is less reflective, and absorbs more sunlight, leading to more warming. Although future changes are uncertain, some of the latest climate models can reproduce the declines in Arctic sea-ice we've already seen. This suggests the models are on track.

Oceans

The oceans absorb large amounts of heat and carbon dioxide from the atmosphere. Ocean currents redistribute heat around the world and affect regional climate. Scientists are getting better at modelling many features of oceans, but some are still poorly represented, such as large-scale narrow currents along coastlines and flow through narrow channels.

Regional predictions

These are much less certain than our estimates for global and large-scale change. This is because even the most advanced global climate models cannot model small features of the Earth system accurately.

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