Choose between climate futures

10 Apr, 2015 12:25 PM
Can we limit the number of future climate scenarios? Are some models more reliable than others?

SOME climate models show that, under high greenhouse gas emissions, Sydney could be up to 4.8C hotter and have 20 per cent less rainfall by 2090. Others show the Harbour City could warm only by 2.3C and become 25pc wetter. How do we deal with such large uncertainty?

The online Australian Climate Futures tool released this week by CSIRO and the Bureau of Meteorology is designed to show projections from up to 40 climate models for different regions, years and emission scenarios. The tool helps select future scenarios so people can plan for climate change.

The tool is part of a new website, with updated climate projections for Australia, that gives unprecedented access to climate change projections data. You can explore the key changes expected in your area through the Regional Climate Explorer.

Climate Futures web tool from CSIRO on Vimeo.

No single future

Climate change projections are presented as a range of possibilities. This occurs because different models produce different outcomes. Even though they are based on the same physical laws, such as conservation of mass, moisture and energy, each climate model treats regional processes in the oceans and atmosphere slightly differently.

These differences pose problems for decision makers who are keen to prepare for climate change. How can we plan for this range of possibilities? Can we limit the number of future climate scenarios? Are some models more reliable than others?

Choose your climate future

If you want to assess the impact of climate change, you need to look at the full range of possibilities.

A projection from a single climate model will not represent the full range of possible futures and impacts. So we need to look at a range of data sets and models. This might seem a daunting task when confronted by up to 40 models, up to four emission scenarios, multiple years and multiple climate variables.

The Climate Futures web tool simplifies the process. It is underpinned by the Climate Futures Framework and the most extensive, independently peer-reviewed climate model evaluation ever undertaken in Australia.

The tool considers three cases: “best case”, “worst case” and “maximum consensus”. It also allows us to compare two different climate variables, such as temperature and rainfall, at the same time. We can further simplify these scenarios into “hotter and drier” or “warmer and wetter”.

For instance, below we have the climate futures of southwest Western Australia, comparing changes from 40 global climate models in temperature and rainfall around 2050 under an intermediate emissions scenario. Most models show a warmer and drier climate (1.5-3.5C warmer, 5-15pc drier). This is the “maximum consensus” future, with almost half (45pc) of the models producing this outcome.

But it is also helpful to think about other climate futures that are less likely but could have a much greater impact. A worst-case scenario for some sectors might be much drier and hotter (more than 15pc less rainfall and 1.5-3C hotter). This future is simulated by 5pc of the models.

A best-case scenario for some sectors might be wetter and warmer, also simulated by 5pc of the models.

For Sydney, Australian Climate Futures shows that by 2030 under high greenhouse gas emissions, more than half the models simulate Sydney’s climate becoming warmer with little change in rainfall (0.5 to 1.5C warmer and less than 5pc change in rainfall).

However, more extreme changes – such as warmer and much drier, or warmer and much wetter – are simulated by a few models. These may be very important in terms of impacts.

The tool also has a feature that helps users select a small number of climate models that represent the “best case”, “worst case” and “maximum consensus” futures. This reduces the effort involved when assessing the impact of climate change. The tool also provides information about model reliability, and warns against using some models in some areas.

Planning for the future

The natural resource management (NRM) community is already using the tool to assist in incorporating climate change into regional strategic plans.

NRM groups are able to use the Climate Futures approach to ensure a range of plausible futures is considered when making, for example, decisions about on-ground options for biodiversity management, or when assessing the opportunities provided by carbon farming schemes to improve regional landscapes.

For example, under the worst-case climate future, an endangered vegetation community may be projected to disappear altogether. To address this would require a large investment – perhaps to translocate species to newly emerging suitable habitats. Under the best case, though, it may be projected to shrink but still remain. This may require lower levels of investment to enhance existing management.

For the maximum consensus future, the expected impacts (and treatment costs) lie between these extremes. Thus planners can weigh this information with social, economic and environmental factors to make informed investment decisions.

The tool and framework have also been successfully applied in the Asia-Pacific region, supporting neighbouring countries to simplify the processes of undertaking climate impact assessments.

Through an extensive Pacific-Australian climate science collaboration, countries like Samoa have used the Pacific Climate Futures tool and associated climate projections to review and update important national infrastructure.

Recently, Pacific Climate Futures was used, along with detailed extreme sea-level modelling, to enable a “climate-proof” design for the new Samoa Parliament Complex.

This article is the second in a series on climate change in Australia, coinciding with the release of new climate websites by CSIRO.

The Conversation

This article was originally published on The Conversation.

Read the original article.

John M Clarke, Penny Whetton, and Tim Erwin all work at the CSIRO

Date: Newest first | Oldest first


10/04/2015 12:48:51 PM

We as Australians can have no influence on the climate, even if we depopulated Australia. Man cannot control the climate of earth!!
10/04/2015 1:48:04 PM

Strange, no models or scenarios for a possible colder climate. History is forgotten, blocked out or re written with adjustments and homogenisation. Ice ages have been before and could happen again, but not in the mind of the AGW faithful.
Rural Realist
10/04/2015 3:04:46 PM

If we really wanted to, we have the geoengineering tools to have very real and significant impacts on the climate of the earth. Sure if Australians acted alone, we couldn't do much to affect the global trend. But the global economy is acting on it (albeit very slowly) and we are going along with it. Neither of which are bad things.
11/04/2015 2:45:46 AM

Humans can indeed and have changed the climate significantly, it is there in the data for those who are curious, sunlight heats the surface of earth, this energy is then radiated back in infrared energy. C02 has intrinsic physical properties which are shown ALL lab tests, one of these properties is to absorb and then emit infrared (heat) radiation, when the infrared is re-emitted it is in a random direction , which approx 50% will not direct to space but back to towards the ground-greenhouse effect-more C02 , more heat. Models are never perfect, ignoring reality (data) is suspicious & immoral.
Simon Anthony
11/04/2015 5:22:19 AM

The facts are in - humans have changed the planetary climate. It changes anyway, an Ice Age is overdue and could possibly be being slowed by our heating effects - this causes instability which results in increased unpredictability - hence the confusion in the models. Simple experiments show the 'Greenhouse' effect - recent history shows the climate instability. There is no downside to changing the way we do things to lessen or reduce human climate impact - as long as we do it soon. We have the knowledge and the tools and more is being developed all the time. It's a government job to enable it
11/04/2015 8:03:39 AM

Peter Walsh may well have consigned this drivel to the trash can and rightly so. Would he not say - modelling, rubbish in and rubbish out.
11/04/2015 8:11:57 AM

Archibald, high-school science will explain to you the greenhouse effect. If we change the composition of the atmosphere, we affect the effect. See: mate-change/climate-science/green house-effect Max, climate models don't show approaching ice ages because they are based on observed reality; models show possible/probable consequences of observed phenomena in a complex system. (It's not a conspiracy, Max.)
12/04/2015 3:47:58 PM

Seems we have moved from reporting factual information to people's (including CSIRO & BOM) daydreams. 40 models with umpteen options blows ones mind as to all the possibilities none of which may prove to be right. They are all full of ifs, buts & maybe's. Some things are true Australia & the southern hemisphere have had & will continue to have no discernible influence on the future climate with or without doing anything about carbon dioxide abatement.
13/04/2015 7:46:02 AM

Science is full of ifs, buts and maybes, daw. It is not a static set of rules. CSIRO and BoM are investigating complex probabilities based on observation. (You would probably complain if they didn't.) See my response to Archibald's statement. If we change the composition of the atmosphere, we - inevitably - change the climate.
13/04/2015 8:52:03 AM

Torobrook , you seem to claim that rubbish went into the modelling . Would you indicate for us the rubbish you are referring to - that would help us assess the signficance (or otherwiise) of what you write.
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