This is a chart of the carbon dioxide levels in the atmosphere over the last 800 000 years, which is as far back as we can trace them. To put you in perspective, in the last 800 000 years, the Earth had already been through many ice ages and the species Homo sapiens was created.
As you can tell from this visual, our current carbon dioxide levels, which are measured in ppm (parts per million) have never have been so high – at least, as far as we can tell. In the last 800 000 years, scientists have noticed that carbon dioxide levels in the atmosphere tend to peak at 300 ppm or less. In fact, it might have been peaking around the time we started burning fossil fuels, during the Industrial Revolution (1800s). Right now, we have more than 400 ppm of carbon dioxide in the atmosphere. What does that mean?
It means that the Earth is getting hotter since carbon dioxide traps heat, that sea levels are rising because of heat expansion, and that more weird phenomena will happen because of the added heat. Global warming means more droughts, more extreme storms, and more ice melt; since all these are linked to the hydrosphere (water), which is greatly affected by the added heat. It also means more famine, more diseases, less fresh water, and more floods; all of these are also linked to the hydrosphere, and any change in the hydrosphere greatly affects us and all of our activities. An increase in greenhouse gases causes a ripple effect throughout the planet and inevitably affects us.
So that is why it is so important to curb our greenhouse gas emissions. Scientists believe that it is important to not exceed the threshold of 350 ppm – which may be a little above what the planet has seen historically, but not too above. At 400 ppm, we are currently off the chart of what the planet considers “normal”- and we are getting even farther. The IPCC 5th Assessment Report estimates that even in the best cases, where everyone agrees to limit their greenhouse gas emissions, we will at least hit 430 ppm at the end of the century (and at the worst, we can even reach 720 ppm – yikes!).
If we reach 450 ppm of carbon dioxide in the atmosphere, we can expect bad things to happen. The temperature would rise at least 2°C above pre-industrial levels. This increase in temperature might not sound too significant, but when the entire planet is taken into consideration, it’s a huge deal. An increase of 2°C in the entire world means major loss of ice, species, fragile ecosystems, land, and weather-related catastrophes.
In all the Climate Conferences and Summits that the Earth has held, not one has resulted in countries agreeing to reduce their greenhouse gas emissions so drastically that the carbon dioxide levels in the atmosphere reaches the “safe ” level (350 ppm). In fact, it’s not even in the IPCC’s predictions. However, in the Paris Agreement in 2015, countries have agreed to not reach the tipping point (450 ppm) and restrain global warming to 1.5°C. Hopefully, countries will stick to this agreement – our future is riding on it.
Dr. James Hansen, former NASA climatologist: “If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced … to at most 350 ppm.”