There is a big hole in climate discourse. Mitigation policy is focussed almost entirely on greenhouse gases (GHGs) ignoring opportunities to cool the panet by increasing vegetation. A paper from the Earth’s Future Journal, A Century of Reforestation Reduced AnthropogenicWarming in the Eastern United States identifies that increased levels of reforestation in the Eastern US has reduce temperatures by up to 1oC. The strongest cooling effect is during midday in the growing season with a 2 to 5o C. cooling differential compared to nearby grassland and croplands. We can assume that this differential will be even greater compared with nearby urban areas. Note that the 1oC. reduction has been happening in the face of global average temperature increases, so the cooling impact of increased forestation might be more like 2oC.
Here is the plain language summary of the article.
A century of eastern US reforestation has had a cooling effect that helps to explain a lack of regional warming in the 20th century, which stands in contrast to warming trends across therest of North America during the same period. Our study shows that forests across much of the eastern UnitedStates have a substantial adaptive cooling benefit for surface temperature, and for the first time, we demonstratethat this benefit also extends to near‐surface air temperature. Therefore, reforestation in temperate zones could provide a complementary set of benefits: mitigating climate change by removing carbon dioxide from the atmosphere, while also helping with adaptation to rising temperatures by cooling surface and air temperatures over large areas.
This news comes as more than 37 cities in India reported temperatures of over 45oC with Dehli recording 52.3oC.
By contrast, in Rajasthan, work to rehydrate the land increased vegetation cover from 2% to 50% and reduced temperatures by 2oC. But unlike the US example, this has not been verified. Here is how rural people in Rajasthan regenerated aquifers, soil, and vegetation, and cooled their region.
So much hot air
Do a quick Google Search and you will find numerous articles about how trees are over-rated in their contribution to cooling the climate. Look a little closer and you will find that they focus on caron sequestration as the mechanism of cooling. Thus trees are relegated as rubbish receptacles for our excessive atmospheric carbon. The people writing these articles would make a greater contribution if they just went outside and planted some trees.
How did we get to this policy myopia? There are some clues in the article Carbon metrics: global abstractions and ecological epistemicide. Our leaders reduce complex phenomena down to numbers to help us understand the world and have targets to pursue. Following the examples of GDP, as a measure of value of an economy and calories, as a measure of value of food, the authors critique the carbon units.
Quantification can be illuminating but it can also act as a blindfold. Like car headlamps on full beam: within the light cone, the view of the road is crystal clear, but outside it the blackness of the night is all the more striking. Seeing the world in carbon units has a similar headlamp effect. If we go over to calculating and comparing all nations and economic activities in carbon units, we become blind to other requirements in ecology and society. Blinded by numbers, we fail to see the diversity of nature, culture and lifestyles – outright epistemicide! What is more, when carbon units are bundled and sold on so-called carbon markets, norms like respect for nature, social cooperation and an individual sense of honour fall by the wayside. (Carbon metrics: global abstractions and ecological epistemicide, p. 8).
Your choice, modelled metrics or observable phenomena?
I suspect on reason that GHGs are central in climate policy are becasue they are relatively easy to model. Recall the sawtooth graph that Al Gore used to illustrate the link between GHGs and temperature increase. The sawtooth variations aligned nicely with seasonal changes in the Northern Hemisphere indicating a relatively even impact of GHGs over seasons. The GHG excluded from these models is water vapour – because it is too hard to model. It differs significantly by location and time of the day. The complex interactions between water, vegetation, soil and other life is ignored.
I agree with Tom Chi on this. We need to reduce emissions, and sequester carbon and support the flourishing of life on earth.
… life on earth, if you follow the algorithm of life on earth you don’t need less of it you need more of it right? What earth has been doing over these billions of years is actually making more life and way more diversity of life you know, touching more and more niches – that is the algorithm of life on planet earth… The whole point is that is what life is trying to do on planet earth and one could design an economy that can go on forever if you focus on the maximisation of organisms benefited in the middle because you can keep on getting more and more economic benefit. (Tom Chi transcript about one hour into his interview avaailable on Nate Hagan’s website. See also this post on Climate Action Tai Tokerau).
Local cooling
Even one tree makes a difference.
Notice how this titoki in central Whangārei is up to 21oC. cooler than the surrounding constructed surfaces. If you want to learn more about local (or direct) cooling see this section on our website and this Wikipedia page on transpirational cooling.
Climate Action Tai Tokerau 
Kia Ora Peter, thanks for this article. It has good points. look at this analysis from chatty which makes it more easily understandable to me: The article highlights a significant gap in climate discourse, emphasizing the heavy focus on greenhouse gases (GHGs) in mitigation policy while largely ignoring the potential cooling effects of increased vegetation. The primary reference is a study from the Earth’s Future Journal which demonstrates that a century of reforestation in the Eastern United States has reduced temperatures by up to 1°C. This cooling effect is especially pronounced during midday in the growing season, showing a 2 to 5°C difference compared to grassland and croplands, and likely even greater compared to urban areas.
Key Points:
Cooling Effect of Vegetation: The study underscores the cooling benefits of reforestation, not just through carbon sequestration but also through direct temperature reduction. This counters the general trend of warming observed across North America, suggesting reforestation as a potent tool for climate adaptation and mitigation.
Comparison with Urban Areas: The cooling effect is particularly significant when comparing forested areas to urban regions, which typically experience higher temperatures due to the urban heat island effect. This implies that increased urban greenery could substantially mitigate local temperature extremes.
Case Study in India: The article contrasts the verified cooling effects in the US with unverified but similar outcomes in Rajasthan, India. In Rajasthan, efforts to rehydrate and increase vegetation cover resulted in a 2°C temperature reduction. This comparison highlights the potential global applicability of reforestation and vegetation increase as climate strategies.
Critique of Carbon-Centric Policies: The article critiques the dominant climate policy focus on carbon metrics, suggesting it blinds policymakers to other ecological benefits and complexities. It argues that by reducing phenomena to numerical targets, important ecological and social dimensions are overlooked.
Observable Phenomena vs. Modelled Metrics: The article advocates for a balanced approach that includes observable phenomena like the direct cooling effects of vegetation alongside modelled metrics like GHG emissions. This holistic view could lead to more effective and comprehensive climate policies.
Support for Life and Biodiversity: Echoing Tom Chi’s perspective, the article underscores the need to support the flourishing of life on Earth. Increasing biodiversity and vegetation aligns with the planet’s natural processes and could yield sustained economic and environmental benefits.
Analysis:
Importance of Reforestation: The study provides compelling evidence that reforestation and increased vegetation can have substantial cooling effects, reinforcing the need to integrate these strategies into broader climate policies. This is particularly relevant as urban areas worldwide grapple with extreme heat events.
Policy Implications: By shifting some focus from GHG-centric policies to include direct cooling strategies like reforestation, policymakers could develop more nuanced and effective climate action plans. This could involve incentivizing urban greenery, protecting existing forests, and promoting large-scale reforestation projects.
Holistic Climate Strategies: The article calls for a more comprehensive approach to climate change, integrating both quantifiable metrics and qualitative ecological observations. This could prevent the narrow focus on carbon sequestration from overshadowing other vital climate mitigation and adaptation strategies.
Educational Value: Highlighting case studies and practical examples like those in the Eastern US and Rajasthan can serve as powerful educational tools. They provide tangible evidence of the benefits of increased vegetation, which could inspire similar initiatives globally.
In conclusion, the article urges a shift in climate policy to embrace the dual benefits of reforestation—carbon sequestration and direct cooling. This approach, combined with traditional GHG reduction strategies, could foster more resilient and adaptable ecosystems, better equipped to handle the challenges of climate change.
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