The composition of the atmosphere is changing
Earth's atmosphere is made up of 78 per cent nitrogen and 21 per cent oxygen. Only about 1 per cent is made up of natural greenhouse gases, but this comparatively small amount of gas makes a big difference. The Industrial Revolution brought new industrial processes, an increase in the burning of fossil fuels, more extensive agriculture, and a rapid increase in the world's population. This rapid increase in human activity led to the (still ongoing) emission of significant amounts of greenhouse gases into the atmosphere. We know this because of measurements made over the past 50 years and the analysis of air bubbles trapped in ancient ice, which show that levels of carbon dioxide, methane, nitrous oxide and halocarbons are increasing.
Although Earth’s atmosphere has changed significantly over geological time, and high concentrations of greenhouse gases have been present in Earth’s atmosphere in the past, never before has Earth been subjected to such a large increase in the amount of greenhouse gases in the atmosphere over such a short time. Although over a geological timeframe (thousands to millions of years), life on Earth would be able to gradually adapt to the increased concentrations of greenhouse gases, the comparative equilibrium that has existed for the past 10,000 years or so is being disturbed at such a rapid rate that adaptation might not be possible.
https://www.science.org.au/curious/earth-environment/enhanced-greenhouse-effect
