The amount of carbon dioxide (CO₂) in our atmosphere, measured in parts per million or “ppm”, provides us with a tangible way to measure global warming trends.  Atmospheric carbon dioxide measurements have been collected directly at Mauna Loa Observatory on the island of Hawai’i for 50 years. 

This graph depicts the steady increase in CO₂ since 1958.

Note that the Earth’s atmosphere held 275 ppm of carbon dioxide up until the early 1700s.  Also note that the 1 degree F increase in global temperature over the last 50 years has been accompanied by an increase in carbon dioxide from 310 ppm to 380 ppm.  

The question of great concern to us is what the future might bring.

Predictions for future CO₂ levels depend on what assumptions are made about human activities that release this gas into the atmosphere. Computer models help us develop reasonable predictions based on different sets of assumptions.  These computer models, generally extrapolating to the end of the century, suggest that the CO₂ concentrations might rise to somewhere between 550 and 1000 parts per million … or more.

It is therefore reasonable to infer that if the 25% increase in CO₂ recorded between 1958 and 2010 resulted in a 1 degree F temperature upswing, the  projected 250% – 300% increase in CO₂ by the end of the century will likely raise global temperatures dramatically. Indeed, models predict an increase between 2.5 degrees F and 10 degrees F, depending on the assumptions.

Clearly, our planet’s future depends on what we do to reduce our greenhouse gas emissions.

Comparison of Past and Potential CO₂ Levels

275 parts per million …
For all of human civilization until about 300 years ago, our atmosphere contained approximately 275 parts per million of carbon dioxide.

350 parts per million …
Many climate scientists and government officials are now saying that 350 parts per million of CO₂ in the atmosphere is a safe upper limit.  Sustained higher levels are likely to lead to positive (self-reinforcing) feedback loops, as additional greenhouse gases are released from warming oceans and vegetation.

400 parts per million …
As the graph below shows, the CO₂ in the Earth’s atmosphere is now 400 parts per million, 50 ppm above the so-called safe level of 350 ppm.  Experts agree that this level cannot be sustained for many decades without potentially catastrophic consequences.

Bringing Carbon Dioxide Back Down to 350 ppm

Dropping CO₂ levels to 350 parts per million will be challenging, but not impossible. To do that, we need to:

• Cut way back on our use of fossil fuels (e.g., coal and oil)

• Switch to solar, wind, and other sources of renewable energy

• Stop deforestation and promote reforestation

• Reduce pollution from agricultural production

• Implement energy efficiency and energy conservation in all aspects of our lifestyles – building, transportation, recreation, city planning, and power generation

• Ensure that nations have support to develop their economies in an ecologically and socially responsible manner.  

If we achieve these objectives, the earth’s soils and forests will slowly cycle some of that extra carbon dioxide out of the atmosphere, and eventually CO₂ concentrations could return to a stable, safe level.

It is impossible to predict how long we have before we experience catastrophic impacts or how long it might take to reduce the atmospheric CO₂ level to 350 parts per million.   What we do know is that the predicted consequences of climate change are already occurring around the world.

While it is too late to escape climate change with only minor impacts, this is not a reason to continue with business-as-usual.  Each and every one of us can make a difference.