A Facebook post claims carbon dioxide emissions are not causing global warming, blaming climate change on the sun rather than human activity.
However, scientists say human actions, such as burning fossil fuels, deforestation and land clearing, are causing increased greenhouse gas concentrations in the atmosphere.
The post, shared on the Australian Climate Sceptics page, makes many claims about global warming, including: “There is no such thing as ‘man-made’ global warming. It is literally impossible for the Earth to ever become a classic greenhouse because of human-based carbon dioxide emissions.”
It adds: “Moreover, the propaganda of ‘man-made global warming’ has made ‘warming’ a bad thing when in fact, climate warming is always good for the Earth …The Sun is the cause of all ‘climate change’.”
The claim is false. Experts told AAP FactCheck increased greenhouse gas concentrations from human activity is causing climate change.
Professor Brendan Mackey, a climate scientist at Griffith University, said the increase in “atmospheric concentration due to human activity is an established scientific fact”.
“This impact is attributable to the so-called ‘greenhouse effect‘ whereby increases in the concentration of specific gases and vapours in the atmosphere, including relatively small changes in CO2 concentrations, cause global warming and subsequent changes to Earth’s climate system,” he said in an email.
Prof Mackey pointed to the Intergovernmental Panel on Climate Change (IPCC), which regularly assesses all aspects of climate change “including how Earth’s climate is changing, including from the influence of human activities, especially the greenhouse gases released into the atmosphere from burning fossil fuel for energy and deforestation and forest degradation.”
“This latest assessment concluded that it is now unequivocal that human influence has warmed the atmosphere, ocean and land, and that widespread and rapid changes in the atmosphere,” he said.
The latest IPCC Assessment Report Summary for Policymakers under the Current State of the Climate A.1.1 states: “Observed increases in well-mixed greenhouse gas (GHG) concentrations since around 1750 are unequivocally caused by human activities. Since 2011 … concentrations have continued to increase in the atmosphere, reaching annual averages of 410 parts per million (ppm) for carbon dioxide,” (page 4).
NASA says evidence for “rapid climate change is compelling” including the planet’s average surface temperature rising, oceans warming, ice sheets in Greenland and Antarctica shrinking, sea levels rising and an increase in extreme weather events.
The European Commission states “burning fossil fuels, cutting down forests and farming livestock are increasingly influencing the climate and the earth’s temperature”, adding a huge amount of greenhouse gases “to those naturally occurring in the atmosphere, increasing the greenhouse effect and global warming”.
The UK Royal Society also says human activity has driven global warming. Its website states scientists “have determined that, when all human and natural factors are considered, Earth’s climate balance has been altered towards warming, with the biggest contributor being increases in CO2.”
Professor Janette Lindesay, a climatology expert at the Australian National University, told AAP FactCheck the post’s claim is false, explaining there’s a direct link between human-caused emissions of carbon dioxide and rising air temperatures.
“Carbon dioxide is a naturally-occurring gas consisting of carbon and oxygen. Together with other atmospheric gases known collectively as ‘greenhouse gases’, carbon dioxide absorbs longwave radiation (heat energy) that would otherwise pass through Earth’s atmosphere to space and leave the planet substantially cooler,” she said in an email.
“Increasing the concentration of greenhouse gases, including carbon dioxide, increases the heat-trapping function of the atmosphere (the enhanced greenhouse effect) and raises the temperature.”
Prof Lindesay said each molecule of carbon dioxide “lasts between 300 and 1000 years once it is in the atmosphere”, meaning the constant emission increase accumulates over the years.
“The natural, pre-industrial concentration of atmospheric carbon dioxide varied between 180 and 280 parts per million during at least the last 800,000 years,” she said.
“The most recent data show that in May 2022 the carbon dioxide concentration, which continues to increase year on year, was 418 ppm (global average at Earth’s surface over the ocean). This rapid increase is due to human, most notably industrial and energy-generating, activities.”
Prof Lindesay said fossil fuel emissions had exceeded emissions from natural sources and were proven due to the chemical difference between atmospheric carbon dioxide from natural and from fossil-fuel sources.
“Fossil fuel emissions, in particular, are effectively one-way; fossil fuel deposits form slowly, over millions of years of geological time,” she said.
“The result is that ongoing fossil fuel emissions – which are indisputably human-caused – continue to build up in the atmosphere. This increases atmospheric trapping of heat, disrupting the balance between incoming solar energy and outgoing energy from Earth’s surface and atmosphere; the result is higher temperatures.”
The claim human-based carbon dioxide emissions do not cause global warming is false. Climate experts told AAP FactCheck greenhouse gas emissions from human activity such as burning fossil fuel and deforestation have exceeded emissions from natural sources. They say emissions of carbon dioxide and other greenhouse gases from human activity accumulate over time, impacting on climate.
False – This claim is inaccurate.