Has human activity caused the world climate to change over the past 100 years?

Answer 1

A careful examination of the data clearly indicates that yes, human activity has indeed contributed significantly to global warming and hence climate change over the past century.

Normal background variations in atmospheric CO2 ranged from 250 to 280 ppm for the past 800,000 years. But beginning with the industrial revolution around 1700, CO2 shot up rapidly from 280 to 290 ppm in just 200 years, about ten times faster than the historical rate of change.

From 1900 to 1950 CO2 rose another 10 ppm, an increase in half a century of the same magnitude in times past took 20 centuries. That is a 40 fold increase over the natural background rate of change.

Within the next two years CO2 will pass 400 ppm, and it will reach 500 ppm before 2050. Earth's temperature is expected to climb 2° to 4° degrees C (4° to 8° Fahrenheit) by 2100.

Answer 2

Yes, human activity, particularly the burning of fossil fuels and deforestation, has significantly contributed to changes in the world's climate over the past 100 years. The increase in greenhouse gases from these activities has led to global warming, resulting in more frequent and severe weather events, rising sea levels, and other impacts on the climate system.