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Even if we halt global warming, local climates will change – and we need new experiments to understand how

Even if we halt global warming, local climates will change – and we need new experiments to understand how

Even if we halt global warming, local climates will change – and we need new experiments to understand how

There’s a big question mark over whether the world will keep global warming below the limits set out in the Paris Agreement. But even if we do, the climate will keep evolving – and society needs to prepare for this.

At the moment, climate models don’t tell us much about a future world in which temperatures have stabilised. As our researchThe paper published today argues that model experiments are required to close this knowledge gap, and better understand the challenges ahead.

In southern Australia, for example, climate change has already led to a number of problems. trendWe are moving towards less rain and more frequent and longer droughts. If the global climate stabilizes, we expect this drying trend will reverse. This could help ease future water supply issues in this region. This would impact urban planning, agriculture, water policy and more.

The new models we’re proposing would enable more useful climate projections aligned with the Paris Agreement targets – and better prepare society for a warmer, but more stable, global temperature.

Stable climate

Under the landmark Paris Agreement, the world is aiming to keep global warming well below 2℃ compared with pre-industrial times, and preferably below 1.5℃.

The world is warming at a rate of around 0.25℃ per decade and is already about 1.2℃ warmerIt is now more than it was in pre-industrial days.

This warming won’t stop until net greenhouse gas emissions are near zero. If we don’t greatly reduce emissions in the next decade, we will warm the planet beyond 1.5℃.

The world has warmed and will continue warming in the coming decades, but the Paris Agreement aims to stabilize the future climate with low global temperature.
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To date, climate simulations used to examine the implications of the Paris Agreement either assume warming continues beyond 1.5℃ and 2℃, or only examine a short period after warming has stopped. These simulations were not designed to assess global warming levels related to the Paris Agreement. They mainly focus on what will occur in the next century.

If we manage to stabilise global temperatures, other aspects of Earth’s climate would continue to change. Studies based on long model experimentsGlobal warming may have slowed ocean and land temperatures, but this suggests that they will continue to rise for centuries. That’s because the ocean warms at a slower rate than the land, and warming water can take hundreds, and even thousands, of years to mix into the deep ocean.

Even after the global temperature stabilises at the levels set out in the Paris Agreement, many ocean areas would likely warm by at least a further 0.5℃. Some land areas would see a cooling effect of 0.5. at least 0.5℃.

The ocean takes time to catch up – and as it does, land temperatures have to fall to maintain the same global average temperature.

Additionally, if the global temperature remained constant, then rainfall patterns would likely be predictable. change. In some subtropical regions, such as southern Australia, this might mean a reversal of the drying trends we’ve seen over the past few decades.

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man stands on ice looking at Arctic scene
The ocean will take time to catch up to global climate change.

We need new models

Clearly, we need new experiments to model Earth’s climate if warming is stabilised at 1.5℃. Our new paperThis framework is designed to help you design these experiments.

Our framework is different from the one used by climate modeling groups around the globe in recent decades.

These groups all used the same projections of greenhouse gas concentrations and how they change over time. This approachIt allows you to compare climate projections between different models for the same scenario of greenhouse gases.

But because each group fed this projection into their own climate model – each with their own characteristics – each produced different predictions for how much global warming would occur. Also, these model simulations are mostly run only to 2100, and so represent a world that’s continuing to warm and hasn’t had time to stabilise.

Instead, our framework aims to achieve the same level global warming across a variety of climate models. This would be achieved by “turning off” the carbon emissions used in various climate models at different times.

So, a climate model that warms more strongly in response to greenhouse gas emissions would have its carbon emissions “turned off” earlier, relative to a slower warming model. This would allow for a group of climate models to simulate global warming at roughly the same level.

Stopping carbon emission will be a great way to reduce them causeGlobal warming will slow down and eventually stop. These simulations can be run for up to 1,000 years after carbon emission stops. This will allow us to study and understand the effects climate stabilisation, in accordance with the Paris Agreement.

A few global modelling centres have started running simulations following similar frameworks, including Australia’s CSIRO. We invite other climate modelling centers to join us in our experiments. This will help policymakers and societies better prepare themselves for a warmer world.

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