Climate change is one of the biggest crises facing humanity. Let's all get a grip on exactly what it is
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| Getty Images / David McNew / Stringer |
Reliable temperature records began in 1850 and our world is now about one degree Celcius hotter than it was in the period between 1850 and 1900 – commonly referred to as the "pre-industrial" average.
The change is even more visible over a shorter time period – compared to average temperatures between 1961 and 1990, 2017 was 0.68 degrees warmer, while 2016 was 0.8 degrees warmer, thanks to an extra boost from the naturally-occurring El Niño weather system.
While this temperature increase is more specifically referred to as global warming, climate change is the term currently favoured by science communicators, as it explicitly includes not only Earth's increasing global average temperature, but also the climate effects caused by this increase.
Global efforts are now focussed on keeping temperatures from increasing more than two degrees above that pre-industrial average, and ideally no more than 1.5 degrees. That goal may still be possible if the international community pulls together.
What are the effects of climate change?
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| Worsening drought conditions are having a major impact on farmers in South Africa's Western Cape region. Morgana Wingard/Getty Images |
It's not only humans that are affected. Warming ocean temperatures are increasing the frequency of coral reef bleaching; warmer, drier weather means that forests in some regions are no longer recovering from wildfires and wildlife habitats around the world are becoming less hospitable to animals.
Climate change is having economic and socio-political effects, too. Food security is already being impacted in a number of African countries and researchers are studying suggestive links between climate change and an increased likelihood of military conflict.
We're already seeing the first climate refugees as people are displaced by rising sea levels, melting Arctic permafrost and other extreme weather.
What are the causes of climate change?
We are. While a wide range of natural phenomena can radically affect the climate, publishing climate scientists overwhelmingly agree that global warming and resultant climate effects that we're witnessing are the result of human activity.
Life on Earth is dependent on an atmospheric "greenhouse" – a layer of gasses, primarily water vapour, in the lower atmosphere that trap heat from the sun as it's reflected back from the Earth, radiating it back and keeping our planet at a temperature capable of supporting life.
Human activity is currently generating an excess of long-lived greenhouse gasses that – unlike water vapour – don't dissipate in response to temperature increases, resulting in a continuing buildup of heat.
Key greenhouse gasses include carbon dioxide, methane and nitrous oxide. Carbon dioxide is the best-known, with natural sources including decomposition and animal respiration. The main source of excess carbon dioxide emissions is the burning of fossil fuels, while deforestation has reduced the amount of plant life available to turn CO2 into oxygen.
Methane, a more potent but less abundant greenhouse gas, enters the atmosphere from farming – both from animals such as cattle and arable farming methods including traditional rice paddies – and from fossil fuel exploration and abandoned oil and gas wells.
Chlorofluorocarbons and hydrofluorocarbons – once widely used in industrial applications and home appliances such as refrigerators – were key greenhouse gasses released during the 20th century, but are now heavily regulated due to their severe impact on the atmosphere, which includes ozone depletion, as well as trapping heat in the lower atmosphere.
Our warming climate is also creating a feedback loop as greenhouse gasses trapped in Arctic permafrost are released.
Why is climate denial a thing?
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| August 29 2017: People wade along a flooded street as cars become stuck during heavy rain in Mumbai. Imtiyaz Shaikh /Anadolu Agency/Getty Images |
This is still playing out in ongoing lawsuits against oil companies, but even giants such as Chevron now publicly acknowledge the role that fossil fuel use has played in changing our climate. Now, their key defence is that it's the fault of fossil fuel consumers for using it, rather than of the companies that extracted, marketed and profited from oil.
Definition of Climate Change
Nasa defines climate change as: "a broad range of global phenomena created predominantly by burning fossil fuels, which add heat-trapping gases to Earth’s atmosphere. These phenomena include the increased temperature trends described by global warming, but also encompass changes such as sea level rise; ice mass loss in Greenland, Antarctica, the Arctic and mountain glaciers worldwide; shifts in flower/plant blooming; and extreme weather events."
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