mapping critical understanding mapping accurate insights formulating calibrated estimations crowdsourcing intelligent predictions delivering precise wisdom mapping the future formulating critical futures calculating quantitative forecasts calculating calibrated predictions formulating precise contingencies delivering predictive futures delivering calibrated futures delivering precise contingencies crowdsourcing precise forecasts


Metaculus Help: Spread the word

If you like Metaculus, tell your friends! Share this question via Facebook, Twitter, or Reddit.

Worst-case scenario for global CO2 levels realized over the coming decades?

In May 2013 the world reacted to a disturbing milestone: Daily averages of atmospheric carbon dioxide hit 400 parts per million (ppm) for the first time in modern history, compared with around 250 parts per million around the time of the Industrial Revolution. Except for a one-day reprieve in late August, daily averages have been above 400 ppm since December 2015. The milestone was noted, analyzed, and mourned by climate scientists who speculated that their children and grandchildren might never again see carbon dioxide concentrations drip below 400 ppm.

Carbon dioxide concentration has been climbing ever since measurements began at Hawaii's Mauna Loa Observatory in 1958. And the climb is accelerating: in the 1960s and 70s, carbon dioxide concentration rose by around 1 ppm per year. Last year the concentration growth rate was 3 ppm per year.

The milestone of 400 ppm is mostly symbolic, but signifies that earth is rapidly approaching the 450 ppm threshold seen by some as a climate stabilization target.

The point at which the global carbon dioxide concentration is projected to reach 500 ppm depends on which so-called "representative concentration pathway" humanity follows. The scenarios range from RCP 2.6, in which CO2 emissions peak and then decline by the mid-21st centry, to RCP 8.5, in which CO2 emissions continue unabated. In the best-case projections, earth never hits 500 ppm, peaking below 450 ppm around 2050. In the worst-case scenario, 500 ppm occurs between 2040 and 2050.

Will earth's carbon dioxide emissions follow the worst-case scenario, reaching a global carbon dioxide concentration of 500 ppm before 2050?

For this question to resolve as positive, the Mauna Loa Observatory must report a monthly carbon dioxide concentration above 500 ppm on or before December 31, 2050.


Metaculus help: Predicting

Predictions are the heart of Metaculus. Predicting is how you contribute to the wisdom of the crowd, and how you earn points and build up your personal Metaculus track record.

The basics of predicting are very simple: move the slider to best match the likelihood of the outcome, and click predict. You can predict as often as you want, and you're encouraged to change your mind when new information becomes available. With tachyons you'll even be able to go back in time and backdate your prediction to maximize your points.

The displayed score is split into current points and total points. Current points show how much your prediction is worth now, whereas total points show the combined worth of all of your predictions over the lifetime of the question. The scoring details are available on the FAQ.

Note: this question resolved before its original close time. All of your predictions came after the resolution, so you did not gain (or lose) any points for it.

Note: this question resolved before its original close time. You earned points up until the question resolution, but not afterwards.

This question is not yet open for predictions.

Thanks for predicting!

Your prediction has been recorded anonymously.

Want to track your predictions, earn points, and hone your forecasting skills? Create an account today!

Track your predictions
Continue exploring the site

Community Stats

Metaculus help: Community Stats

Use the community stats to get a better sense of the community consensus (or lack thereof) for this question. Sometimes people have wildly different ideas about the likely outcomes, and sometimes people are in close agreement. There are even times when the community seems very certain of uncertainty, like when everyone agrees that event is only 50% likely to happen.

When you make a prediction, check the community stats to see where you land. If your prediction is an outlier, might there be something you're overlooking that others have seen? Or do you have special insight that others are lacking? Either way, it might be a good idea to join the discussion in the comments.