Science – Human role in climate warming

I was recently finalising a discussion with my physio in Warkworth about my fitness when the conversation turned to what was I doing for the remainder of my day. I explained that I was preparing a community talk on solutions to climate change. She indicated that she was concerned about climate change but had a basic question. How do we know that humans caused climate change? I explained that this question was very straight forward and could be understood from a single chart published widely by the USA National Aeronautical and Space Administration (NASA), which has international responsibility for monitoring climate change. I referred her to the following link summarizing the NASA evidence for human factors in climate change, and to the first chart in that link: https://climate.nasa.gov/evidence/. I would certainly urge anyone who is uncertain about the human role in climate change to check out this very simple and clear explanation.

The NASA chart shows the rise and fall in carbon dioxide levels in the earth’s atmosphere over the past 800,000 years. Carbon dioxide is the product of burning or combustion of carbon-containing materials including coal, petroleum, natural gas, biomass etc. Carbon dioxide naturally absorbs infrared (warming) radiation at several “fingerprint” energies, and this leads to the CO2 molecule warming up. The amount of carbon dioxide in the atmosphere increases because of the combustion of fossil fuels. Hence, we get atmospheric warming which leads to ocean warming and increased atmospheric moisture, more severe storms and flooding. Over land masses, climate warming leads to extreme temperatures, drought, starvation, famine, climate refugees and inevitably to conflict and eventually war. The United Nations Development Program predicts that by 2100 there will be 85 million refugees in Africa seeking food for survival.

The NASA chart shows that carbon dioxide levels have risen and fallen over more the 800,000 years. This pre-historic natural climate change is not the climate change that NASA and science generally are concerned about. Modern humans (Homo sapiens) have been present for less than 300,000 years. The global concern about climate warming begins at the onset of the industrial revolution about 1850 when humans started increasingly to use coal in transportation, firstly in the transition from sail to steam and, later, in the international expansion of coal-powered rail systems. In the 20th century, petroleum became the main fuel for road transportation and air travel and later natural gas (methane) provided grid electricity. All these technical developments have contributed large quantities of carbon dioxide to the atmosphere.

The almost vertical diversion of atmospheric carbon emissions in the NASA chart starting from 1850 is the result of the ongoing surge in the use of fossil fuels over the last 170 years. This is the period of real Climate Change that threatens human existence, especially in poorer countries, which will not have the economic capacity to adapt to the rapid change. A recent research report from a Canadian University predicted that the climate change will lead to one billion extra deaths within the next century. Climate warming since 1850 that has been caused by humans using fossil fuels, is now the most serious threat humanity has faced.