By 2500, Earth Will Be Alien to Humans if We Don't Act Now, Scientists Warn

Many reports that are based on scientific research discuss the long-term effects of climate change, such as the rising levels of greenhouse gases and temperatures. For example, the Paris Agreement requires that we limit global warming to below 2.0 degrees Celsius above preindustrial levels by the end the century.
Since 1990, the Intergovernmental Panel on Climate Change (IPCC), has evaluated our progress using its scientific assessment reports and other special reports. The IPCC reports evaluate existing research to determine where we stand and what we need before 2100 to reach our goals.

According to the United Nations Assessment of Nationally Determined Contributions (NDCs), current government promises could lead to a dangerous 2.7 degree Celsius increase in temperature by 2100. This would mean unprecedented fires, storms droughts floods and heat as well as profound land- and aquatic ecosystem changes.

Although some climate projections look beyond 2100, they are not being considered in mainstream climate adaptation or environmental decision-making. This is not surprising, given that people born today will be in their 70s by 2100. How will their children and grandchildren see the world?

Researchers and policymakers need to look beyond the 2100-horizon in order to grasp, plan, and communicate the full spatial, temporal, and global impact of climate impacts under any scenario.

After 2100

Will the climate stop warming by 2100? What does this mean for humanity now and in the future? These questions are answered in our open-access article published in Global Change Biology.

Global climate model projections were run based on Representative Concentration Pathways, which are "time-dependent projections for atmospheric greenhouse gas (GHG).

Our projections modeled low (RCP6.0), medium and high mitigation scenarios (RCP4.5), which correspond to the Paris Agreement goal of "well-below two degrees Celsius" up to the year 2000.

To get an idea of what environmental challenges children and their descendants may face in the future, we also modelled the distribution of vegetation, heat stress, and growing conditions of our major crop plants.

(Lyon et al., 2021)

Above: The global mean near-surface temperature (solid lines), and the thermosteric sea rise (dotted lines), anomalies relative to 2000-19 for the RCP6.0 and RCP4.5 scenarios. The shaded regions indicate the nominal reference years and time horizons of particular interest. The bottom panel displays spatial anomalies relative the 2000-19 mean for 2100, 2200, and 2500 climates in the three RCPs.

Our model showed that the global average temperature keeps rising above 2100 in both RCP4.5 (6.0) and 6.0. These scenarios result in vegetation moving towards the poles and the most suitable areas for certain crops being reduced. Some areas with a long history of ecosystem and cultural richness, such as the Amazon Basin may become barren.

We also found that heat stress can cause death in areas of tropical high population. These areas could become uninhabitable. Even in high-mitigation situations, sea level continues to rise due to the expansion and mixing of water in warmer oceans.

Our findings, although they are based only on one climate model show that they are within the range projections from other models and help reveal the potential scale of climate change on longer timescales.

To really portray what a low-mitigation/high-heat world could look like compared to what we've experienced until now, we used our projections and diverse research expertise to inform a series of nine paintings covering a thousand years (1500, 2020, and 2500 CE) in three major regional landscapes (the Amazon, the Midwest United States and the Indian subcontinent).

Images for the year 2500 are centered on RCP6.0 projections. They include slightly more advanced, but easily recognizable versions of current technologies.


(Lyon et al., 2021/CC BY-ND)

Above: The top photo shows an Indigenous village pre-contact (1500 CE), with access to the river, and plants in the rainforest. The middle image shows a modern landscape. The bottom image depicts 2500 years ago. It shows a barren landscape with low water levels and a degraded infrastructure.

Midwest US

(Lyon et al., 2021/CC BY-ND)

Above: This painting depicts pre-colonial Indigenous communities and communities that were built and have a variety of maize-based agricultural practices. The second image is of the same area today with large harvesters and a monoculture of grain. However, the last image shows agriculture adaptation to a hot, humid subtropical climate. It is based on oil palms, and arid zone succulents. With a lower human presence, the crops are managed by AI drones.

Subcontinent of India

(Lyon et al., 2021/CC BY-ND)

Above: A busy scene in an agrarian village of rice planting, livestock usage and social life is shown in the top image. The second image shows a modern scene that combines traditional rice farming with modern infrastructure found in many parts of the Global South. Bottom image depicts a future with heat-adaptive technologies, including robotic agriculture and green building without the need to have people around.

An alien future?

Between 1500 and now, we've witnessed colonization, the Industrial Revolution, modern identities, institutions, and mass combustion of fossil fuels.

We must stop climate warming. The Earth will be affected in 500 years. This will impact our ability to sustain many basic needs, especially in the culturally and geographically rooted cultures that provide meaning and identity.

Our high-end projections of Earth are alien to us. We have two choices: reduce emissions and adapt to the warming that we can't escape, or consider living on an Earth different from this one.

Christopher Lyon, postdoctoral researcher in Natural Resource Sciences, McGill University. Alex Dunhill is Research Fellow in Palaeobiology at University of Leeds. Bethany Allen is a PhD student, School of Earth and Environment. James McKay is Manager, Centre for Doctoral Training. Julien Riel-Salvatore is Professor of Anthropology, University of Montral. Lindsay C. Stringer and Rob Marchant are Professors of Tropical Ecology, University of York. Tracy Aze works as an Associate Professor, Earth and Environment and Geography, University of York.

This article was republished by The Conversation under Creative Commons. You can read the original article.