Our changing climate

Climate change isn’t a new phenomenon, but what’s unusual is the rate and scale of change – and its causes.

Changes in the world’s climate have always occurred, due to a range of geological, biological, atmospheric, oceanographic and astronomic factors.

There have been periods of extremes in the distant past. But there’s wide scientific consensus that the climate variations seen over the last 150 years are due to human activity as well as natural factors.

Left unchecked, climate change will speed up, with significant impacts for nature, economy and society here in Scotland and globally.

We must plan for these changes – to try to overcome the negative impacts and to benefit from new opportunities where we can.

Drivers of climate change

The cause of climate change is widely agreed to be the growing emissions of greenhouse gases associated with human activity.

Global mean surface temperatures are rising as greenhouse gases – mainly carbon dioxide (CO2), methane and nitrous oxide – build up in the atmosphere. The ‘greenhouse effect’ causes the heat to be trapped.

Fossil fuel combustion (plus a smaller contribution from cement manufacture) is responsible for more than 75% of CO2 emissions caused by humans. Land use change, mainly large-scale clearance of tropical rainforest, is responsible for the other 25%.

Natural carbon stores are a growing concern. Peatland habitats are vast stores of carbon when in good condition. But they become another source of greenhouse gases when they degrade.

Greenhouse effect

Some of the Sun’s radiation that penetrates the Earth’s atmosphere is absorbed by the Earth’s surface, heating it up. This is ‘shortwave radiation’.

Some of this energy is then re-irradiated (or bounced back) towards space at longer wavelengths. But part of this ‘outgoing longwave radiation’ is absorbed by greenhouse gases and re-irradiated in all directions – including towards the Earth’s surface again.

The result is that some of the thermal energy is trapped in the lower atmosphere, heating it up.

This is the natural greenhouse effect. It helps to keep the mean surface temperature on Earth at about 15ºC (it would otherwise be about –18ºC).

But the higher the concentration of greenhouse gases in the atmosphere, the greater the warming. Human activities are warming the planet more than would occur naturally. This is sometimes called the enhanced greenhouse effect.

Scotland’s future climate

Scotland has relatively warm, wet winters and cool, wet summers – especially in the west – compared to other places at a similar latitude. Mountains increase our range of climatic conditions, with near-arctic conditions on peaks.

But our climate is already changing and will continue to do so for many decades to come – even with substantial emissions reductions in place.

The factors that control the Earth’s climate interact in complex ways, so it’s very hard to predict exactly how the climate will change. But the consensus is that temperatures will continue to rise globally.

We expect Scotland to have warmer, wetter winters and hotter, drier summers.

As the climate changes, Scotland is likely to experience:

  • more extreme weather events
  • more long heat spells
  • higher maximum temperatures across the country
  • fewer days of snow and frost
  • longer periods of dry weather in the spring and summer
  • much more rain on the wettest days of the year