Climate change explained

What is climate change?

Climate change is a large-scale, long-term shift in the planet’s weather patterns or average temperatures.

What’s the greenhouse effect?

Great question – and bonus points if you mumbled something about it ‘being related to greenhouses’.

The greenhouse effect was given that name precisely because it works like greenhouses do. Essentially, incoming ultraviolet light passes easily through glass to be absorbed by the plants inside as heat. Yet the outgoing radiation is much weaker. It can’t get back through the glass walls – so it’s trapped inside, creating a warm atmosphere.

Earth’s atmosphere is the same. It’s wrapped in a layer of ‘greenhouse gases’ that keep the planet warm. A nice combination of incoming and outgoing radiation. But keeping these equal is a delicate balancing act. For a long time, it’s been like Goldilocks’s optimum porridge – just right. Not too hot, and not too cold. Which is ideal for sustaining so many different life forms (unlike other planets in our solar system that are either scorching or freezing). And naturally, we want it to stay that way.

Obviously the incoming radiation is mainly generated by the sun, in the form of visible light, plus invisible types, like ultraviolet (UV) and infrared (IR). But surprisingly, nearly a third of this is immediately reflected back out into space. By clouds, sand, ice, snow, and any other reflective surfaces.

It’s why some experts trying to lessen the impact of global warming suggest we whitewash roofs and use light-coloured materials to surface roads and pavements.

The rest of the incoming radiation? Well that’s absorbed into the sea, land, and air, heating them up. They release this heat as infrared thermal radiation, and try sending it back into space. But because it can’t escape – you guessed it – the world gets warmer.

What are the causes of climate change?

Big cloud of smoke coming out of a power plant chimney, polluting the air with greenhouse gases

An increase in greenhouse gases is to ­blame, say scientists – and they know about this stuff.

Unfortunately, human activity is creating too many greenhouse gases, creating an enhanced greenhouse effect. It’s adding to the insulation of the planet, warming it overall and causing climate changes we can’t predict.

Humans still burn coal and oil – which creates carbon emissions – and cut down trees that absorb carbon dioxide. The result? An increasing number of greenhouse gases in the atmosphere. The more there are floating about, the thicker the layer around the Earth becomes, and the higher the average temperature of the planet becomes.

Most scientists agree recent changes can’t be explained by natural causes alone. This side of the scientific community suggests human activity is responsible for recent global warming.

Climate change means:

  • Changes in rainfall.

  • Rising sea levels.

  • Melting ice caps.

  • Changes in nature.

Burning fossil fuels for energy releases carbon dioxide (CO2) – one of the most potent greenhouse gases – into the atmosphere.

Main fossil fuels:

  • Coal

  • Natural gas

  • Oil

Adding insult to injury, people are still chopping down forests and woodlands like there’s no tomorrow.

It’s a dangerous combination of behaviours: trees and green spaces have historically acted as greenhouse gas ‘sponges’, soaking up CO2 during photosynthesis.

The amount of CO2 in the atmosphere has increased dramatically since the industrial revolution. If we continue abusing resources to the extent we do, the planet will continue to swelter.

What are the effects of global warming?

Mother Earth has seen plenty of fluctuations between tropical climates and ice ages throughout her 4.5-billion-year history. But Earth’s average temperature is now rising unnaturally. Knock-on effects include changing weather patterns, melting ice caps, rising sea levels and changes to ecological environments.

Climate change and the weather

Floods, heat waves, hurricanes... Scientific research is telling us that climate change is having an extreme effect on weather systems worldwide. There’s certainly a link between human-induced climate change and the ‘biblical’ weather the planet endured in 2017 (to put a price tag on it – in the US alone, financial costs in the aftermath of that year exceeded an eye-watering $300bn).

These clever scientists are continually working on Earth System Models to accurately study environmental changes. In the UK, the Met Office and the Natural Environment Research Council work on an ESM together to get answers.

ESMs help in:

  • Enabling society to respond urgently to global climate change

  • Predicting regional and local impacts of environmental change

  • Creating and supporting other research communities

Climate change and infectious diseases

Zika virus in blood with red blood cells. Researchers say climate change may accelerate the outbreak of infectious disease like Zika.

Researchers say climate change may accelerate the outbreak of infectious disease, such as the exceedingly unpleasant dengue fever, malaria and Zika. Deforestation, monsoon rainfall and high humidity all enhance mosquito breeding, and survival. Recent analysis reveals the malaria risk increases 'around five-fold' in the year after an El Niño event.

Unfortunately, water-borne illnesses like cholera and diarrhea also follow drought and heavy rainfall.

At sea, disease comes in the form of 'red tide' algae, which produces powerful toxins. These can kill fish, shellfish, mammals, and birds, and potentially cause illness in humans. Sadly, ocean warming creates these types of algal blooms.

Severe drought in northern Kenya has brought about an epidemic of cholera, and malaria has finally arrived in East Africa's highland regions, where the disease has never existed before.

Being able to associate diseases with climate change is a complex business. Thankfully, researchers are working on just that, to better meet the challenges ahead.

Climate change and coastal living

Due to global warming, the UN has warned us of a temperature increase of 3.2°C by 2100 – this will dramatically change the world's coastline. And probably, your favourite beach.

If this happens, these coastal cities will be first to be flooded:

  • Osaka, Japan

  • Alexandria, Egypt

  • Rio de Janeiro, Brazil

  • Shanghai, China

  • Miami, US

As Bill Patzert, celebrated oceanographer and former NASA research scientist puts it:

“We’re living in a warmer world. We’re living in a melting world. And of course, the unequivocal evidence is that sea levels are rising." He says, "We’re living risky. We’re living too close to the coast.”

Climate change and food security

Droughts, floods and extreme weather can destroy crops, along with the infrastructure to farm them. Crop prices may rise as a result of climate change, while yields fall, affecting the world's most vulnerable (and hungry) people.


Climate change and biodiversity

Polar bear mother with two cubs on an ice flow in the ocean, symbolic for the climate change situation in the arctic

Recent scientific studies show many species, which define biodiversity, are expected to decline as temperatures continue to rise. This will directly affect the Earth’s ecosystems and biodiversity. The thawing of ice packs is already shrinking the habitats of Arctic creatures, and drought and changes in rainfall threaten creatures inland. The Intergovernmental Panel on Climate Change says a 1.5°C average rise may put a tragic 20-30% of species at risk of extinction.


When will we experience the full weight of climate change?

Our oceans have absorbed over 90% of the excess heat trapped by greenhouse gas emissions. Scientists have charted the extent of this, concluding the sea has warmed consistently over the last 50 years, at 0.12°C per decade.

Experts suggest 2°C of warming is the planet's tipping point – meaning change is then irreversible. Dr Ken Caldeira, atmospheric scientist at the Carnegie Institution for Science says, "There is a 93% chance that global warming will exceed 4°C by the end of this century". Gulp.

A 2017 article published by researchers at Utrecht University in the Netherlands tells us, "studies indicate that there will be a dangerous anthropogenic interference with climate by the end of this century". In other words, humans will pollute the planet. A lot.

According to the National Oceanic and Atmospheric Administration (NOAA), Carbon dioxide levels rose 3 parts per million (ppm) to 405.1 ppm in 2016, putting CO2 at its highest levels in over 10,000 years! It first went above 400 ppm in 2015, which scientists called the “point of no return.

So, we could argue that the turn of the next century is when humans feel the true brunt of it all. Although those devastated by of one of 2017's many natural disasters might disagree...

Why are some people sceptical about climate change?

Well, some believe climate change is simply part of planet Earth’s natural ebb and flow, that our planet is a self-regulating organism. Sounds reasonable. After all, over the course of its 4.5 billion-year life, earth has weathered tropical climates and ice ages many times, right? Since the last ice age – around 11,500 years ago – the climate has been relatively stable. Until now that is.

Can climate change be stopped or reversed?

If we’re smart, climate change could be paused, to an extent. And if we can stop it, perhaps reversing it – also referred to as drawdown – could follow. The drawdown plan suggests 100 ways we can go about it. Interestingly, 80 of these solutions should kick in between 2020 and 2050. If these work, we could potentially begin a reversal as of then. Let’s hope so.

What are we doing to combat climate change?

The United Nations have come together to create the Paris Agreement to combat global warming. It’s kind of a big deal. The agreement, for the first time, "brings all nations into a common cause to undertake ambitious efforts to combat climate change."

Its aim, is to keep the "global temperature rise this century well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius."

The US and China are officially the world's biggest polluters; The then President, Barack Obama, signed an executive order (bypassing congress) for the US to join the agreement on the same day as China did: 3rd September, 2016.

However, President Trump pulled out of the deal in June 2017. Trump commented he was “elected to represent the citizens of Pittsburgh, not Paris.”

As a result, the US is currently the only nation to refuse the historic agreement.

Currently, 196 of the 197 countries involved have signed. The Paris Agreement entered into force on 4 November 2016.

What can I do to help fight climate change?

Ticked box on ballot paper and pen

Here are 5 ways you can make a real difference:

  • At the polls, vote for politicians with environmental policies you believe in. Have your say in how your community and your country is run, and effect change.

  • Fly less, and rather than drive, use trains and public transport more. If you do drive, consider an electric vehicle, or look into car-sharing. Try to walk or cycle where possible.

  • Eat less meat, which affects energy consumption in a big way. Choose local or organic products whenever possible. If you can’t go veggie like Jeremy Corbyn, at least take Barack Obama’s advice and “have a smaller steak.”

  • Save power: reuse, repair, and recycle as much as you can – the UK’s carbon footprint of clothing alone has risen to more than 26m tonnes of CO2 a year.

The major greenhouse gases, as listed by the Centre for Climate and Energy Solutions:  

Greenhouse gas Chemical formula Anthropogenic Sources Atmospheric Lifetime (years) GWP (100 year time horizon)
Carbon Dioxide CO2 Fossil-fuel combustion, Land-use conversion, Cement Production 100 1
Methane CH4 Fossil fuels, Rice paddies, Waste dumps 12 25
Nitrous Oxide N2O Fertilizer, Industrial processes, Combustion 114 298
Tropospheric Ozone O3 Fossil fuel combustion, Industrial emissions, Chemical solvents hours-days N/A
CFC-12 CCL2F2 Liquid coolants, Foam 100 10,900
HCFC-22 CCI2F2 Refrigerants 12 1,810
Sulfur Hexoflouride SF6 Dielectric fluid 3,200 22,800


Visit the Center for Climate and Energy Solutions site to find further references and extra information – and view this table in its original form.

Interested in learning more about greenhouse gases and how they affect our planet? Explore the Met Office Climate Guide pages.

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