Earth's temperature has changed over the years. However, human activity is the largest contributing factor to global warming.
Ian Plimer, an Australian geologist, addressed the U.K. parliament in 2017 and claimed that global warming and climate change are natural reoccurring processes. Plimer is known to be a climate change denier. Since COP26, a U.N. conference on climate change, some social media posts have quoted Plimer and said that claims of climate change and global warming are a hoax. Global warming is the rise in the average temperature of the Earth's air and oceans. It is often described as the most recent example of climate change. According to National Geographic, the Earth's temperature has changed multiple times over the years. Past changes in Earth's temperature happened very slowly. However, the recent warming trend is much faster than it ever has been. Natural cycles of warming and cooling are not enough to explain the amount of warming the planet experienced in such a short time; only human activities can account for it. The Intergovernmental Panel on Climate Change (IPCC) developed a report stating that the leading cause of the drastic increase in the Earth's temperature is human activity. "It is unequivocal that human influence has warmed the atmosphere, ocean, and land," the report stated. NASA released a consensus report about human's contribution to climate change. The change in the Earth's temperature over the past 800,000 years was due to slight variations in the Earth's orbit, affecting how much solar energy the planet receives. However, recent temperature trends are not due to the Earth's orbit. 95 percent of current warming is due to human activity. Natural emissions, such as volcanic activity, do not emit as much carbon dioxide compared to human activity. Pew Research Center's study about how global warming has increased over generation observed that the last and the current generation contributed approximately two-thirds of the present-day carbon dioxide-induced warming. As it takes a long time to remove carbon dioxide from the atmosphere, global mean temperatures are expected to increase by several tenths of a degree for at least the next 20 years, even if carbon dioxide emissions were immediately cut to zero.