Article by Natalie Fleming, based on Walter Jehne’s presentations. A link to Jehne’s original lecture appears at the end of the article.
The global climate crisis is intensifying, with extreme weather events like floods, droughts, wildfires, and storms becoming increasingly frequent and severe. While reducing carbon dioxide (CO₂) emissions has been the primary focus of climate action for decades, Walter Jehne, an internationally recognised Australian climate scientist and microbiologist, argues that this approach overlooks the fundamental role of the water cycle in regulating Earth’s climate.
Jehne advocates for a paradigm shift: instead of concentrating solely on CO₂, we must restore the Earth’s hydrological systems through regenerative land management practices to achieve rapid climate cooling.
For over half a century, since Charles Keeling’s 1958 discovery of rising atmospheric CO₂ levels, global efforts have centered on reducing emissions from fossil fuels. This focus, while important, has led to economic stalemates and delayed meaningful action. Jehne contends that this narrow emphasis neglects the immediate and dangerous threat posed by hydrological extremes—events directly linked to disruptions in the water cycle. These extremes are not mere projections but present realities reshaping our landscapes, economies, and communities.
The water cycle
Jehne emphasises that to effectively address these challenges, we must understand the water cycle’s central role in Earth’s climate system. Although CO₂ contributes to the greenhouse effect, it accounts for only about 4 per cent of Earth’s heat dynamics. In stark contrast, water vapor and hydrological processes regulate approximately 95 per cent of the planet’s heat dynamics. This discrepancy highlights a critical oversight in both climate policy and science.
Earth maintains a delicate heat balance by receiving about 342 watts per square meter (W/m²) of solar radiation and radiating the same amount back into space. Human activities have disrupted this balance, causing the Earth to retain an additional 3 W/m² of energy—less than 1 per cent of the total incoming solar radiation. While seemingly small, this imbalance drives global warming. Jehne proposes that by restoring natural hydrological processes, we can correct this imbalance and achieve rapid climate cooling.
The water cycle comprises several interconnected processes that collectively regulate Earth’s temperature. One key process is transpiration and evaporation, which acts as nature’s air conditioning system. Plants absorb water from the soil and release it as vapor through transpiration, cooling the land as water evaporates. This process transfers about 24 per cent of incoming solar energy back into the atmosphere. Currently, we have only about 50 per cent of the vegetation cover that existed 10,000 years ago. Jehne argues that increasing vegetation cover by just 4 per cent could offset the excess heat caused by human activities, demonstrating the significant impact of re-greening efforts.
Another critical aspect is the formation of humid hazes due to pollution. Air pollutants like dust, aerosols, and particulate matter provide surfaces for water vapor to condense into tiny droplets, forming humid hazes that trap heat and contribute to atmospheric warming. These hazes can absorb up to 20 per cent of incoming solar radiation regionally. Reducing air pollution minimises haze formation, allowing for better cloud formation and enhancing the atmosphere’s ability to reflect heat.
Cloud formation plays a pivotal role in cooling the planet. Clouds form when water vapor condenses around condensation nuclei—tiny particles like sea salt, ice crystals, or biological particles such as bacteria. Clouds cover about 50 per cent of Earth’s surface at any given time and reflect approximately 33 per cent of incoming solar radiation back into space. Enhancing cloud formation through land management practices increases Earth’s cooling capacity.
Rainfall formation depends on the presence of precipitation nuclei. Biological particles from forests, such as bacteria and fungal spores, serve as highly effective precipitation nuclei, promoting rainfall. Protecting and restoring forests enhances the release of these particles, improving rainfall patterns and supporting the hydrological cycle.
Soil moisture and vegetative cover are essential for controlling soil temperature. Vegetation shades the soil and promotes moisture retention, keeping soil temperatures low. Bare soils can reach temperatures up to 70C (158F), re-radiating significant heat into the atmosphere. Maintaining continuous vegetative cover prevents soil overheating and decreases the amount of heat entering the atmosphere.
At night, the Earth’s surface emits long-wave radiation back into space. High atmospheric moisture content can trap this heat, preventing cooling. Increased atmospheric water vapor from disrupted hydrological cycles has led to higher nighttime temperatures, accounting for 60 per cent of observed global warming. By enhancing rainfall and reducing excess atmospheric moisture, we can reopen these radiation windows, allowing for effective nighttime cooling.
The soil carbon sponge
Central to Jehne’s proposal is rebuilding the soil carbon sponge—a porous, carbon-rich soil structure that retains water, supports plant growth, and enhances the water cycle. Each gram of soil carbon can hold up to 20 grams of water. A healthy soil sponge increases the soil’s capacity to retain moisture, supporting vegetation even during dry periods. Rich in organic matter, the soil sponge fosters microbial activity that breaks down nutrients, making them available to plants. Improved soil structure allows for deeper root systems, enhancing plants’ access to water and nutrients.
Soil microbes and fungi play a crucial role in this process. They decompose organic matter, converting it into stable soil carbon (humus), which builds the soil sponge. Mycorrhizal fungi form symbiotic relationships with plant roots, enhancing nutrient uptake and water absorption. Fungi also decompose forest litter, reducing fuel loads and preventing wildfires. Shifting ecosystems from fire-dominated to fungi-dominated systems increases resilience.
For over 420 million years, plants and microbes have worked together to pull carbon from the atmosphere, building rich, fertile soils. By adopting regenerative practices that emulate these natural systems, we can rapidly restore soil health and ecosystem function.
Jehne also highlights additional key components in ecosystem management:
- Polycultures and biodiversity are essential. Diverse plant communities create resilient ecosystems, improving soil health and stabilising local climates.
- Holistic grazing and animal integration, when managed properly, can help regenerate grasslands, improve soil structure, and increase carbon sequestration. Grazing animals stimulate plant growth, aid in seed dispersal, and enhance soil carbon through manure deposition.
- The biotic pump is another critical concept. Large forests act as biotic pumps, creating low-pressure zones that draw moist air from oceans inland, promoting rainfall. Deforestation disrupts this process, leading to aridification.
- Rehydration techniques for degraded lands, such as building swales and planting vegetation to reduce runoff, restore the soil sponge and reverse desertification.
- Maintaining ground cover enhances the albedo effect—vegetation reflects more sunlight than bare soil, reducing heat absorption and contributing to surface cooling.
- Oceans play a significant role as well. They release sea salt aerosols that serve as cloud condensation nuclei, influencing cloud formation and climate. Protecting marine ecosystems supports the global water cycle and climate regulation.
- Agroforestry and perennial systems integrate trees with crops and livestock, enhancing biodiversity, sequestering carbon, and improving soil health. These systems are more resilient to climate extremes and contribute to long-term carbon storage.
Jehne outlines a comprehensive plan to restore the water cycle and cool the planet:
- Increase urban and regional green cover by planting trees and creating green spaces reduces urban heat islands and enhances transpiration.
- Prevent wildfires through fungal and soil management reduces wildfire risks and supports forest health.
- Promote urban agriculture to increase local food security, build soil carbon, and foster community engagement.
- Support village and community agriculture to enhance food sovereignty, improve rural livelihoods, and restore ecosystems.
- Restore degraded lands by employing rehydration techniques and preventing overgrazing reverses desertification and stabilises local climates.
- Revise government metrics and policies to incorporate environmental and social costs into economic measures, encouraging sustainable development and aligning economic incentives with ecological health.
- Foster eco-innovation and enterprise to drive technological advancements, create green jobs, and accelerate the adoption of regenerative practices.
- Expand regenerative agricultural practices to sequester carbon, improve soil health, and increase resilience to climate extremes.
Jehne stresses that we have a critical window of about ten years to implement these changes. Delaying action risks crossing ecological tipping points, leading to irreversible climate impacts and widespread ecosystem collapse. While reducing CO₂ emissions is necessary, Jehne emphasises that it is insufficient on its own due to buffered systems like oceans that regulate atmospheric CO₂ levels. Hydrological management offers a more immediate solution by directly influencing Earth’s heat dynamics.
By restoring the water cycle through regenerative practices, we can achieve rapid climate cooling, providing the time needed to transition away from fossil fuels without catastrophic consequences. Jehne’s blueprint for climate action is rooted in understanding and working with natural systems. By focusing on the water cycle and the myriad processes that regulate Earth’s climate, we unlock powerful solutions that are both effective and sustainable.
Restoring the soil carbon sponge, enhancing biodiversity, managing land holistically, and rehydrating landscapes are not just environmental imperatives—they are essential strategies for ensuring human survival and well-being. The path forward requires collective effort and a willingness to embrace complexity. Governments, communities, and individuals must work together to implement these solutions, recognising that our future depends on the health of the planet’s ecosystems.
The opportunity to restore Earth’s climate balance is within our grasp. By taking immediate action to regenerate our ecosystems, we can secure a sustainable and prosperous future for generations to come. Embracing the complexity of ecosystem management—incorporating soil microbes, fungi, plant diversity, animal integration, and hydrological restoration—is essential. These elements, when combined, provide the tools needed to stabilise and cool the Earth’s climate rapidly.
Let us seize this critical moment to implement Walter Jehne’s visionary blueprint. By restoring the Earth’s hydrological systems through regenerative land management, we can not only mitigate the impacts of climate change but also foster a thriving, resilient planet for all forms of life.
Click here for the Climate Landscapes website and to watch Walter’s Jehne’s lecture