{"id":1875,"date":"2021-11-17T13:06:03","date_gmt":"2021-11-17T13:06:03","guid":{"rendered":"https:\/\/horizon.peachpuff-wolverine-566518.hostingersite.com\/?p=1875"},"modified":"2021-11-17T13:06:03","modified_gmt":"2021-11-17T13:06:03","slug":"scientists-improving-the-crystal-ball-for-better-climate-predictions","status":"publish","type":"post","link":"https:\/\/scienceblog.com\/horizon\/1875\/scientists-improving-the-crystal-ball-for-better-climate-predictions\/","title":{"rendered":"Scientists improving the \u2018crystal ball\u2019 for better climate predictions"},"content":{"rendered":"
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Climate models are used to predict how the climate will likely respond to rising greenhouse gas concentrations in the coming decades, a timescale crucial to meeting the terms of the Paris Agreement. That\u2019s why it\u2019s necessary to keep developing and refining such models to better support climate policies.<\/strong><\/p>\n<\/div>\n<\/div>\n

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What will Earth be like in 50 or 100 years? To make such predictions, the closest thing we have to a crystal ball is data.<\/p>\n

\u2018Climate models help make sense out of the current state of the climate,\u2019 said Dr Debbie Rosen, an environmental scientist at the University of Leeds. \u2018They can also be used to understand how the climate changed in the past, and for predicting what this means for the future.\u2019<\/p>\n

The terms of the Paris Agreement, adopted by 196 parties in 2015, were discussed at the Glasgow COP26 summit from 31\u00a0October to 12\u00a0November 2021. \u2018With data, policymakers can enact effective responses, such as the recent report published by the UN\u2019s Intergovernmental Panel on Climate Change (IPCC) working group,\u2019 said Pierre Friedlingstein, a professor of earth system science at the University of Exeter.<\/p>\n

According to Friedlingstein, policymakers need two numbers. First, they need to know how much carbon humans can emit before it\u2019s too late to reduce fossil fuel emissions and meet the 2\u00b0C target of the Paris Climate Agreement. Second, they need to know how fast emissions must be reduced if we are to stay below the 2\u00b0C threshold. \u2018We get these numbers using climate models,\u2019 he said.<\/p>\n

One such model, newly developed by the CONSTRAIN<\/a> project, has demonstrated that the effects of human-induced warming can be untangled from the effects of natural warming on much shorter timescales than previously thought possible. The model will also improve our understanding of how much the world will eventually warm if atmospheric carbon dioxide levels double from those of pre-industrial times.<\/p>\n

With this information, one can predict, for instance, how different cuts in emission levels could affect the speed of global warming over the next two decades. \u2018We hope this information will guide some of the decisions made at COP26 itself, but also help those working on climate adaptation and mitigation in planning their post-COP26 activities,\u2019 said Dr Rosen, who coordinates the CONSTRAIN project.<\/p>\n

Closing in on calculations of the carbon cycle<\/strong><\/p>\n

Of course, climate models haven\u2019t always been so advanced. It was only when earth system models (ESMs) began to feature in research that scientists could integrate the interactions of systems such as the atmosphere, oceans, land, ice and the biosphere into climate modelling. An ESM is a coupled climate model that includes the movement of carbon through the earth system.<\/p>\n

\u2018These more advanced models represent the coupling between the climate system and the carbon cycle,\u2019 noted Friedlingstein. \u2018As a result, we can now use models to estimate the state of regional and global climate under a wide variety of conditions.\u2019<\/p>\n

As Friedlingstein explained, to determine how much carbon can be released before we hit a specified temperature increase (i.e. 2\u00b0C), one needs to first calculate how much of the carbon is being absorbed by natural carbon sinks like the ocean<\/a>, and how much is going into the atmosphere.<\/p>\n

To illustrate, let\u2019s consider that an increase in emissions results in an increase in the amount of carbon dioxide (CO2) going into the oceans. For a variety of reasons, any increase in the amount of CO2 entering the ocean could negatively impact its ability to act as a carbon sink. \u2018If the ocean absorbs less carbon, this means more CO2 will be put into the atmosphere, which ultimately means more global warming,\u2019 observed Friedlingstein. \u2018Climate models must incorporate this data.\u2019<\/p>\n

Although the CO2-carbon cycle and climate-carbon cycle feedbacks have been identified for more than a decade, scientists have yet to fully quantify these feedbacks. They also need to be able to confidently attribute past changes in the carbon cycle; this is key to being able to anticipate its future evolution.<\/p>\n

\u2018There is an urgent need to better understand and better model the processes that drive the observed variability in atmospheric CO2 at seasonal-to-century timescales,\u2019 stressed Friedlingstein. \u2018This is how we improve climate projections and better inform climate mitigation and adaptation.\u2019<\/p>\n

Meeting this need is the 4C<\/a> project, which is led by Friedlingstein. 4C scientists are using innovative methods and new observations to increase confidence in \u2013 and reduce uncertainty about \u2013 using ESM models. In so doing, they are helping improve the ability of these models to assess and predict carbon cycles and their impact on future climate change.<\/p>\n

\u2018For the first time, we are able to predict the evolution of global carbon cycle variability over the coming decade, including atmospheric CO2, land and ocean carbon sinks, and climate response,\u2019 noted Friedlingstein. \u2018This information will prove critical to tracking our overall progress towards meeting the Paris Agreement goals.\u2019<\/p>\n

Don\u2019t neglect nitrogen\u2019s role<\/strong><\/p>\n

While enhancing ESMs\u2019 ability to factor in carbon cycle variability represents a step change in terms of climate forecasting, there\u2019s still more room for improvement, which is where the CRESCENDO<\/a> project comes in.<\/p>\n

\u2018Our goal is to provide a clear picture of the magnitude of global climate change and, in particular, how much carbon humans can still emit if we wish to keep global warming below certain levels,\u2019 said CRESCENDO project leader, Colin Jones, who is a National Centre for Atmospheric Science (NCAS) senior scientist and professor at the University of Leeds.<\/p>\n

The inclusion of nutrient nitrogen\u2019s role in the various ESM terrestrial carbon cycle models is one of the project\u2019s most important developments. \u2018It is generally assumed that the photosynthetic uptake of CO2 by forests and plants will increase as the amount of CO2 in the atmosphere increases,\u2019 explained Jones. \u2018While this is true, plant growth is also limited by other factors such as the availability of water, nutrients, and most importantly, nitrogen.\u2019<\/p>\n

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Because ESMs fail to include the role of nitrogen when calculating the Earth\u2019s photosynthetic uptake of CO2, they miss a key control on future carbon uptake. \u2018This means our estimates of how much carbon humans could release to stay below key warming targets is preliminary, at best,\u2019 noted Jones.<\/p>\n

Thanks to CRESCENDO\u2019s efforts, numerous ESMs now include this important process. \u2018This means our model estimates of future uptake of CO2 by the terrestrial biosphere are more realistic,\u2019 added Jones. \u2018This is a critical piece of knowledge required by policymakers for forming climate change mitigation plans with respect to the \u201cwhen and how much\u201d of reducing CO2 emissions.\u2019<\/p>\n

The models have spoken \u2026 now it\u2019s time to act<\/strong><\/p>\n

We have the models, and we have the data. The question is, do we have the will to make the changes required to meet the Paris Agreement goals?<\/p>\n

According to Friedlingstein, we have to make headway. \u2018We\u2019ve been saying what is going to happen for 30\u00a0years, and what we said was going to happen is now happening,\u2019 he pointed out. \u2018The governments have agreed, it\u2019s time to act.\u2019<\/p>\n

Even if we miss our initial targets, Friedlingstein stressed the need to push on in the right direction and not lose momentum. After all, even a 2.5\u00b0C threshold is better than doing nothing. \u2018If our climate models show one thing for sure, it is that any action is better than no action at all,\u2019 he urged.<\/p>\n

The research in this article was funded by the EU. If you liked this article, please consider sharing it on social media.<\/p>\n<\/div>\n<\/div>\n

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See also<\/h2>\n