The United Nations Intergovernmental Panel on Climate Change (IPCC) released the first major report as part of its sixth assessment of global climate science — the first significant analysis of research since 2014, covering more than 14,000 studies. Its core finding: global warming of 1.5°C (2.7 °F) over pre-Industrial Revolution levels is inevitable over coming decades, but if we act now, we can stave off further, more dangerous warming of 2°C (3.6°F), or, even worse, 3°C (5.4°F), which is what the world is now on a trajectory to experience. As climate reporter Andrew Revkin notes, humans are currently adding “40-billion-plus tons of greenhouse gases to the atmosphere each year (and rising).” The IPCC argues that limiting warming to 1.5°C is only possible if the world’s governments accelerate efforts to reduce emissions by transitioning to renewable energy and net-zero communities and transportation systems. “Achieving global net-zero carbon dioxide emissions is a requirement for stabilizing carbon dioxide-induced global surface temperature increases.”
In this first comprehensive analysis of physical sciences, which was approved by 195 governments, the IPCC states that “many of the changes observed in the climate are unprecedented in thousands, if not tens of thousands, of years.” Analyzing the IPCC’s findings, The New York Times reports that “the last decade is quite likely the hottest the planet has been in 125,000 years. Atmospheric levels of carbon dioxide have not been this high in at least 2 million years.”
To date, the report finds, “emissions from human activities are responsible for approximately 1.1°C (2°F) of warming since 1850-1900.” If the world can achieve “immediate, rapid and large-scale reductions in greenhouse gas emissions” in the near term, climate change could be stalled at a 1.5°C increase. And 1.5°C of warming, while dire, will be far less destructive than 2°C.
“For 1.5°C of global warming, there will be increasing heat waves, longer warm seasons, and shorter cold seasons. At 2°C of global warming, heat extremes would more often reach critical tolerance thresholds for agriculture and health.” A 2°C temperature increase would force almost unimaginable adaptations and migrations.
High-level findings from the IPCC highlight the need to rapidly reduce greenhouse gas emissions but also scale up climate adaptation efforts and plans to retreat from soon-to-be uninhabitable areas. Landscape architects not only help communities reduce emissions by planning and designing low-carbon transportation systems and applying Climate Positive Design; they also engage with communities on nature-based adaptation and retreat plans.
According to the IPCC, warming is occurring across all parts of the planet, but most in the Arctic and on land.
The impacts of climate change also already go beyond warming to include “changes to wetness and dryness, to winds, snow and ice, coastal areas, and oceans.” Climate change is intensifying the water cycles, which will lead to more intense rainfall and flooding but also more intense drought. In higher latitudes, there will likely be more rain, while it will decrease in the sub-tropics, which will get even hotter.
This is where landscape architects can plan and design nature-based solutions. In areas of higher flooding, landscape architects plan and design green infrastructure or sponge city approaches that safely retain stormwater; in areas experiencing drought, they design sustainable landscapes that collect and reuse water and reduce water use.
The IPCC finds that the high end of temperatures and heatwaves have increased due to human-driven greenhouse gas emissions. “It is virtually certain that hot extremes (including heatwaves) have become more frequent and more intense across most land regions.”
Research has found that the parks landscape architects plan and design can reduce nearby community temperatures by at least 6°F degrees. Communities with streets lined with shade trees are also up to 10°F cooler during the daytime.
Seas, which have risen 8 inches over the past century, are expected to continue to rise, causing more frequent and severe flooding in low-lying areas and increased erosion and coastal habitat loss. “Extreme sea level events that previously occurred once in 100 years could happen every year by the end of this century.”
This is where landscape architects and planners are helping communities either manage retreat and relocation or become far more resilient to flooding through nature-based approaches. Landscape architects, planners, and ecologists are also helping to create room for coastal species at risk to migrate and adapt.
Since 1993, the rate of warming in oceans has doubled, and oceans will continue to experience “more frequent marine heatwaves, ocean acidification, and reduced oxygen levels. These changes affect both ocean ecosystems and the people that rely on them.” Coastal and indigenous communities at risk will need further support from landscape architects in adapting their way of life and livelihoods.
The IPCC indicates that the loss of seasonal snow cover, glaciers and ice sheets, and Arctic sea ice is expected to accelerate. Artic sea ice is at its lowest levels since at least 1850. The temperatures of Arctic and Boreal permafrost have also increased, heightening risks of releasing billions of tons of stored carbon dioxide and methane, a potent greenhouse gas. Landscape architects can help increase the health and resilience of Artic ecosystems by reducing man-made impacts that further disturb these soils.
Lastly, the IPCC finds that the effect of climate change in cities, where 56 percent of the global population now resides, “may be amplified, including heat (since urban areas are usually warmer than their surroundings), flooding from heavy precipitation events, and sea level rise in coastal cities.”
With the help of landscape architects and planners, cities are applying resilient green infrastructure or sponge city approaches that combat both increased heat and flooding at once.