predicting critical insights generating predictive insights computing predictive understanding generating definitive wisdom assembling intelligent futures mapping the future formulating critical understanding crowdsourcing intelligent estimations delivering contingent predictions crowdsourcing quantitative wisdom assembling definitive predictions predicting calibrated wisdom assembling definitive contingencies crowdsourcing predictive insights

Question

Metaculus Help: Spread the word

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

3.6°C global warming by 2100?

Without additional efforts to reduce GHG emissions beyond those in place today, global emissions growth is expected to persist, driven by growth in global population and economic activities. Global mean surface temperature increases in 2100 in baseline scenarios—those without additional mitigation—range from 3.7°C to 4.8°C above the average for 1850–1900 for a median climate response.

Given these estimates of the baseline scenarios of unmitigated emissions, studies exploring particular effort-sharing mitigation frameworks, have estimated substantial global financial flows associated with mitigation in scenarios to limit warming during the 21st century to less than 2°C. But there is also a non-negligible chance that unmitigated emissions will lead to global temperature increases much higher than the median estimated outcome. More generally, estimates of temperature increases resulting from greenhouse emissions have a “fat” right tail, meaning that there is a low, but non-negligible chance of very high temperature increases.

In particular, it has been argued that there is a decent chance that the unmitigated emissions might result in a >6.4ºC change in global mean surface temperature. Then, even with the systems to reduce temperatures by 2.8ºC (as might be required in baseline scenarios to achieve the 2ºC target), mean global temperature might be still be at least as high as 3.6ºC, despite substantial mitigation efforts.

The estimated humanitarian impacts of climate changes are likely highly nonlinear: marginal temperature increases are expected to cause more damage at already-increased temperatures (i.e. going from 3ºC to 4ºC is expected to be significantly worse than going from 1ºC to 2ºC). According to the IPCC's 2014 report,

The risks associated with temperatures at or above 4°C include severe and widespread impacts on unique and threatened systems, substantial species extinction, large risks to global and regional food security, consequential constraints on common human activities, increased likelihood of triggering tipping points (critical thresholds) and limited potential for adaptation in some cases.

Will there, by 2100, have been a period of at least 5 consecutive years, in which the average global temperature in each year was at least 3.6˚C greater than the average global temperature relative to the period 1861–1880?

Data for resolution shall come from NASA, if possible. Note that the data in the link is normalised relative to the 1951-1980 baseline, on which 1880 stands at -0.2. Therefore, the critical value to look for with this specific NASA dataset will be 3.4˚C. It is likely, though, that the link will no longer be active in a few decades, so a different dataset may have to be used anyway.

{{qctrl.predictionString()}}

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.