We know that behind the extreme events such as hurricanes, flooding, drought, and even wildfires that have become ever more common over the past few years is a rise in global temperatures. This can also be seen in changing local climates and especially in ocean temperatures. The rise in global temperature from the pre-industrial baseline is currently estimated at about one degree Celsius and it could reach 4 degrees Celsius by 2100. This would be devastating to human civilization as sea levels rise and weather patterns become ever more extreme and unpredictable.
How do we stop this rise, and can we eventually reverse it?
The link between human activities and the rise in temperatures is the change in atmospheric composition, primarily an increase in carbon dioxide, which acts as a greenhouse gas. Before the Industrial Revolution, carbon dioxide made up about 280 parts per million of the atmosphere, and we are now at about 400 ppm. Greenhouse gases allow solar radiation to reach the surface of the Earth but prevent the re-emission of heat, and there are other greenhouse gases which are also influential. The effect of each gas can be measured in terms of how it traps heat, and in how long it persists in the atmosphere. In addition to carbon dioxide, significant greenhouse gases include methane, nitrous oxide, and various refrigerants. The effects of these various gases are measured as carbon dioxide equivalent based on the global warming potential or GWP.
Relative effects and persistence:
Global Warming Potential
Lifetime in years
To take action against climate change we need to reduce the production or release of these greenhouse gases and accelerate removal from the atmosphere. That means we need to understand where they come from. The primary source of carbon dioxide is burning fossil fuels such as coal, oil, and natural gas. The sources of methane include oil and gas production, agriculture, and releases from thawing permafrost. Nitrous oxide is released from fertilizers and industry. Refrigerant gases are released during production and use. So we can look at our activities in order to understand which greenhouses gases those activities produce, directly or indirectly.
How do you measure the impact of a company (or an individual, for that matter) on climate change?
We’ll discuss that next time.
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