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The Science

What is climate change?

The Earth’s average temperature is about 15C but has been much higher and lower in the past. There are natural fluctuations in the climate but scientists say temperatures are now rising faster than at many other times. This is linked to the greenhouse effect, which describes how the Earth’s atmosphere traps some of the Sun’s energy. Solar energy radiating back to space from the Earth’s surface is absorbed by greenhouse gases and re-emitted in all directions. This heats both the lower atmosphere and the surface of the planet. Without this effect, the Earth would be about 30C colder and hostile to life. Scientists have proven however that we are adding to the natural greenhouse effect, with gases released from industry and agriculture trapping more energy and increasing the temperature. This is known as climate change or global warming. The greenhouse gas with the greatest impact on warming is water vapour. But it remains in the atmosphere for only a few days. Carbon dioxide (CO2), however, persists for much longer. It would take hundreds of years for a return to pre-industrial levels and only so much can be soaked up by natural reservoirs such as the oceans. Most man-made emissions of CO2 come from burning fossil fuels. When carbon-absorbing forests are cut down and left to rot, or burned, that stored carbon is released, contributing to global warming. Since the Industrial Revolution began in about 1750, CO2 levels have risen more than 30%. The concentration of CO2 in the atmosphere is higher than at any time in at least 800,000 years. Other greenhouse gases such as methane and nitrous oxide are also released through human activities but they are less abundant than carbon dioxide. These gases in the atmosphere are trapping more and more heat making or planet warmer, the higher temperatures impact other weather systems and the Earth’s entire climate is altered drastically.

How do we know its real?

The world is about one degree Celsius warmer than before widespread industrialisation, the World Meteorological Organisation (WMO) says. The 20 warmest years on record all occurred in the past 22 years, with 2015-18 making up the top four. Across the globe, the average sea level increased by 3.6mm per year between 2005 and 2015. The rate in the last two decades, however, is nearly double that of the last century and is accelerating slightly every year. Most of this change was because water increases in volume as it heats up. However, melting ice is now thought to be the main reason for rising sea levels. Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa. And satellite records show a dramatic decline in Arctic sea-ice since 1979. The Greenland Ice Sheet has experienced record melting in recent years. Satellite data also shows the West Antarctic Ice Sheet is losing mass. A recent study indicated East Antarctica may also have started to lose mass. Data from NASA’s Gravity Recovery and Climate Experiment show Greenland lost an average of 286 billion tons of ice per year between 1993 and 2016, while Antarctica lost about 127 billion tons of ice per year during the same time period. The rate of Antarctica ice mass loss has tripled in the last decade. Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent. This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans. The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year. The effects of a changing climate can also be seen in vegetation and land animals. These include earlier flowering and fruiting times for plants and changes in the territories of animals. The evidence is overwhelming and what is mentioned here barely scratches the surface of the effects of climate change we’ve seen so far. Climate change is a fact and it is an issue we need to deal with.

What impacts will it have?

Local

The impacts of climate change will vary around the world. Here in Scotland and the UK we can expect to see sea levels rise, covering low lying areas, in particular east England. Droughts and floods become more likely across the country as extreme weather increases, putting people’s lives and homes at risk. There would also be an increased demand for water in hotter summers puts pressure on water supplies. Climate change is the single greatest threat to Scotland’s habitats, whether they’re found on our mountain tops or our seabeds. Some habitats will be directly affected. More often, climate change will alter the intricate ecological balances that let plants and animals grow and thrive. Many of Scotland’s species are highly adapted to specific climatic conditions, meaning that climate change will have drastic effects.

 

Global

How much time do we have left?

How do we fix this problem?

Resources for learning more:

Sources:

BBC

NASA

National Geographic 

IPCC

United Nations