Our climate projections for 2500 show anEarth that is alien to humans27 September 2021, by Christopher Lyon Et Al

Current climate future predictions do not go far enough.Credit: Shutterstock

There are many reports based on scientificresearch that talk about the long-term impacts ofclimate change—such as rising levels ofgreenhouse gases, temperatures and sealevels—by the year 2100. The Paris Agreement,for example, requires us to limit warming to under2.0 degrees Celsius above pre-industrial levels bythe end of the century.

Every few years since 1990, we have evaluatedour progress through the Intergovernmental Panelon Climate Change's (IPCC) scientific assessmentreports and related special reports. IPCC reportsassess existing research to show us where we areand what we need to do before 2100 to meet ourgoals, and what could happen if we don't.

The recently published United Nations assessmentof Nationally Determined Contributions (NDCs)warns that current promises from governments setus up for a very dangerous 2.7 degrees Celsiuswarming by 2100: this means unprecedented fires,storms, droughts, floods and heat, and profoundland and aquatic ecosystem change.

While some climate projections do look past 2100,these longer-term projections aren't being factored

into mainstream climate adaptation andenvironmental decision-making today. This issurprising because people born now will only be intheir 70s by 2100. What will the world look like fortheir children and grandchildren?

To grasp, plan for and communicate the full spatialand temporal scope of climate impacts under anyscenario, even those meeting the Paris Agreement,researchers and policymakers must look wellbeyond the 2100 horizon.

Global mean near-surface air temperature (solid lines)and thermosteric sea level rise (dotted lines) anomaliesrelative to the 2000-19 mean for the RCP6.0, RCP4.5and RCP2.6 scenarios. Shaded regions highlight the timehorizons of interest and their nominal reference years.The bottom panel shows spatial anomalies relative to2000-19 mean for the 2100, 2200 and 2500 climatesunder the three RCPs. Credit: Lyon et al., 2021

After 2100

In 2100, will the climate stop warming? If not, whatdoes this mean for humans now and in the future?In our recent open-access article in Global ChangeBiology, we begin to answer these questions.

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We ran global climate model projections based on Representative Concentration Pathways (RCP),which are "time-dependent projections ofatmospheric greenhouse gas (GHG) concentrations." Our projections modeled low (RCP6.0), medium(RCP4.5) and high mitigation scenarios (RCP2.6,which corresponds to the "well-below 2 degreesCelsius" Paris Agreement goal) up to the year2500.

We also modeled vegetation distribution, heatstress and growing conditions for our current majorcrop plants, to get a sense of the kind ofenvironmental challenges today's children and theirdescendants might have to adapt to from the 22ndcentury onward.

The Amazon: The top image shows a traditional pre-contact Indigenous village (1500 CE) with access to theriver and crops planted in the rainforest. The middleimage is a present-day landscape. The bottom image,considers the year 2500 and shows a barren landscapeand low water level resulting from vegetation decline,with sparse or degraded infrastructure and minimalhuman activity. Credit: Lyon et al., 2021, CC BY-ND

In our model, we found that global averagetemperatures keep increasing beyond 2100 underRCP4.5 and 6.0. Under those scenarios, vegetationand the best crop-growing areas move towards thepoles, and the area suitable for some crops isreduced. Places with long histories of cultural andecosystem richness, like the Amazon Basin, maybecome barren.

Further, we found heat stress may reach fatallevels for humans in tropical regions which arecurrently highly populated. Such areas mightbecome uninhabitable. Even under high-mitigationscenarios, we found that sea level keeps rising dueto expanding and mixing water in warming oceans.

Although our findings are based on one climatemodel, they fall within the range of projections fromothers, and help to reveal the potential magnitudeof climate upheaval on longer time scales.

Midwest U.S.: The top painting is based on pre-colonisation Indigenous cities and communities withbuildings and a diverse maize-based agriculture. Thesecond is the same area today, with a grain monocultureand large harvesters. The last image, however, showsagricultural adaptation to a hot and humid subtropical

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climate, with imagined subtropical agroforestry based onoil palms and arid zone succulents. The crops are tendedby AI drones, with a reduced human presence. Credit:Lyon et al., 2021, CC BY-ND

To really portray what a low-mitigation/high-heatworld could look like compared to what we'veexperienced until now, we used our projections anddiverse research expertise to inform a series ofnine paintings covering a thousand years (1500,2020, and 2500 CE) in three major regionallandscapes (the Amazon, the Midwest UnitedStates and the Indian subcontinent). The imagesfor the year 2500 center on the RCP6.0 projections,and include slightly advanced but recognizableversions of today's technologies.

The Indian subcontinent: The top image is a busyagrarian village scene of rice planting, livestock use andsocial life. The second is a present-day scene showingthe mix of traditional rice farming and moderninfrastructure present in many areas of the Global South.The bottom image shows a future of heat-adaptivetechnologies including robotic agriculture and greenbuildings with minimal human presence due to the needfor personal protective equipment. Credit: Lyon et al.,

2021, CC BY-ND

Between 1500 and today, we have witnessedcolonization and the Industrial Revolution, the birthof modern states, identities and institutions, themass combustion of fossil fuels and the associatedrise in global temperatures. If we fail to halt climatewarming, the next 500 years and beyond willchange the Earth in ways that challenge our abilityto maintain many essentials for survival—particularlyin the historically and geographically rootedcultures that give us meaning and identity.

The Earth of our high-end projections is alien tohumans. The choice we face is to urgently reduceemissions, while continuing to adapt to the warmingwe cannot escape as a result of emissions up tonow, or begin to consider life on an Earth verydifferent to this one.

This article is republished from The Conversationunder a Creative Commons license. Read the original article.

Provided by The Conversation

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APA citation: Our climate projections for 2500 show an Earth that is alien to humans (2021, September27) retrieved 25 November 2021 from https://phys.org/news/2021-09-climate-earth-alien-humans.html

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