Sentences with phrase «by human activity relative»

He wants to know, please tell us what percentage of carbon dioxide is caused by human activity relative to other sources of carbon dioxide.

Not exact matches

Even allowing for the relative strength of the effects, CO2 is still responsible for two - thirds of the additional warming caused by all the greenhouse gases emitted as a result of human activity.

Based on an extensive literature review, we suggest that (1) climate warming occurs with great uncertainty in the magnitude of the temperature increase; (2) both human activities and natural forces contribute to climate change, but their relative contributions are difficult to quantify; and (3) the dominant role of the increase in the atmospheric concentration of greenhouse gases (including CO2) in the global warming claimed by the Intergovernmental Panel on Climate Change (IPCC) is questioned by the scientific communities because of large uncertainties in the mechanisms of natural factors and anthropogenic activities and in the sources of the increased atmospheric CO2 concentration.

So really forced = external and unforced = internal both terms relative to a specific system, but either is «natural variability» not driven by human activity.

The summary related aviation's role relative to all human influence on the climate system: «The best estimate of the radiative forcing in 1992 by aircraft is 0.05 W m — 2 or about 3.5 % of the total radiative forcing by all anthropogenic activities.»