This Is the Easy Part

In1990, the Intergovernmental Panel on Climate Change (the UN’s scientific working group on global warming) wrote the following:

We are certain of the following: there is a natural greenhouse effect which already keeps the Earth warmer than it would otherwise be; emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases…

[Gases like carbon dioxide] would require immediate reductions in emissions from human activities of over 60% to stabilize their concentrations at today’s levels; methane would require a 15–20% reduction….

Under the IPCC Business-as-Usual (Scenario A) emissions of greenhouse gases, a rate of increase of global-mean temperature during the next century of about 0.3°C per decade (with an uncertainty range of 0.2°C to 0.5°C per decade); this is greater than that seen over the past 10,000 years. This will result in a likely increase in global-mean temperature of about 1°C above the present value by 2025 and 3°C before the end of the next century.

Here