(Photo : Marcin Jozwiak) Carbon dioxide levels in the atmosphere fluctuate significantly over the year, with some being consumed by plants in the northern hemisphere throughout the spring and summer before rising again throughout the autumn and winter. However, human activity, mainly by the combustion of fossil fuels and deforestation, is responsible for the long-term trend of increasing carbon dioxide concentrations, according to the Met Office. Decrease in Global Emission (Photo : Getty images ) As a result of a downturn in transportation usage and economic activity due to the coronavirus pandemic, global emissions decreased briefly in 2020. However, the 2020 pollution reductions were insufficient to significantly reduce carbon dioxide accumulation in the atmosphere, which continues to climb.