Scientists and politicians say that planet Earth is facing a crisis because of climate change. The evidence for this needs to be considered, as does the assertion that it is being caused by humans.
Planet Earth has been warming rapidly since the dawn of the Industrial Revolution and the average temperature at the Earth’s surface has risen about 1.1°C since 1850. Each of the last four decades has actually been warmer than any that preceded it, since the middle of the 19th Century.
These observations come from analyses of millions of measurements gathered in different parts of the world, and multiple independent teams of scientists have reached the same result … a spike in temperatures coinciding with the onset of the industrial era.
In terms of understanding how humans are responsible for global warming, greenhouse gases, which trap the Sun’s heat, are the crucial link between temperature rise and human activities.
CO₂ is the main culprit for trapping the Sun’s energy. Satellites show less heat from the Earth escaping into space at precisely the wavelengths at which CO₂ absorbs radiated energy. Burning fossil fuels and chopping down trees, activities that exploded after the 19th Century led to the release of this greenhouse gas.
Climate models have been used to show what would have happened to temperatures without the massive amounts of greenhouse gases released by humans. They reveal there would have been little global warming – and possibly some cooling – over the 20th and 21st Centuries, if only natural factors had been influencing the climate.
Human-induced warming leaves scientists with certain expectations. These include the rapid melting of the Greenland and Antarctic ice sheets, an increase in the number of weather-related disasters, and the continuing rise of global sea levels.
The value of forests may have been significantly underestimated when considering climate change. Forests act as carbon sinks, absorbing CO₂ from the atmosphere.
Deforestation, primarily for agriculture, logging, and urbanisation, reduces the Earth’s capacity to absorb CO₂, contributing to increased atmospheric concentrations.
The absorption of excess CO₂ by the oceans leads to ocean acidification, which can harm marine ecosystems, including coral reefs and shellfish populations.
For many years, groups of so-called climate sceptics have cast doubt on the scientific basis of global warming. However, virtually all scientists who publish regularly in peer-reviewed journals now agree on the current causes of climate change.
A 2021 UN report said it “is unequivocal that human influence has warmed the atmosphere, oceans and land”. The level of heating Earth has experienced already is predicted to cause significant changes to the world around us.