With fires, storms, record-breaking temperatures and changes in the natural environment, there is growing evidence that our earth’s systems are becoming increasingly unstable. This has potentially catastrophic consequences.
Public debate often places climate risks in the context of “this century” or “by 2100”. But scientists are increasingly highlighting the risks of devastating and irreversible impacts in just 20 or 30 years. This is within our lifetimes, and certainly within our children’s.
These risks include:
Loss of nearly all corals, which support 25% of all ocean life (as documented in the recent film Chasing Coral)
Collapsing ice sheets, which will raise sea-levels, devastating coastal cities and low-lying countries
Warming oceans, which energize storms (to category 6 and higher), with damage that includes breaches of coastal nuclear reactors
Warming of the planet, caused by the greenhouse effect, is the primary stressor of many of these environmental challenges. Carbon dioxide and other pollutants present further complications, such as increasing ocean acidification.
450 parts per million
Humans have long affected their environment. But until we started burning fossil fuels in the mid-1800s, the amount of carbon we added to the air balanced the amount removed. However, over the past 150 years, CO2 emissions have far outpaced the subtractions. Our annual production of carbon is currently around 40 billion tonnes.
Scientists debate how much carbon can be safely stored in our atmosphere before exceeding safe operating limits. The United Nation’s Intergovernmental Panel on Climate Change (IPCC) estimates it to be around 300 billion tonnes, but many scientists suggest a much lower amount.
Climate scientists believe that a CO2 concentration of 450 parts per million is likely to warm the climate by 2°C, the safe upper limit. By 2015, CO2 in the atmosphere rose to 400 parts per million. At our current rate of emissions, we will reach 450 ppm within 20 years.
Even if we achieve the Paris Agreement reductions in greenhouse gas emissions, the gases that were generated over the past few decades will be absorbed back into the earth slowly, and will be at an elevated level in our atmosphere for hundreds, if not thousands, of years.
To stay below the safe threshold of 2°C, the UN and IPCC plans entail removal of CO2 from the atmosphere using methods that do not exist yet (“negative emissions”).