Trees as air conditioning

 Hat tip to Christoph Chorherr

[In German; Google translation below]

"Ein ausgewachsener Laubbaum kann an einem heißen Sommertag etwa 300 bis 500 Liter Wasser verdunsten. Bei einer Verdunstung von 400 Litern pro Tag entspricht das einer Kühlenergie von ca 270 kWh" Zum Vergleich. Das entspricht 4-6 kleineren Klimaanlagen (je 2-3 Kw Kühhleistung." orf.at/stories/3427...

"A mature deciduous tree can evaporate approximately 300 to 500 liters of water on a hot summer day. At an evaporation rate of 400 liters per day, this corresponds to a cooling energy of about 270 kWh."

For comparison, this is equivalent to 4-6 small air conditioners (each with 2-3 kW cooling capacity).

See also The magic of trees

Before and after

From a toot by Qagggy

BEFORE & AFTER: There are so many smart cities like this. It makes you wonder why there are still so many…how do I put this delicately? …dumb ones.

Before

After
Notice how the hideous windows in the building at the end of the street
have been restored to their original beauty!

Cooling cities down with fountains?

 An interesting article in the Guardian

The secret to more livable, cooler Australian cities may lie with the ancient Romans and a network of fountains like the Trevi and those in Piazza Navona, a new report on tackling urban heat has found.

Rome has a network of 2,000 fountains which draw huge crowds daily to enjoy their cooling effects in the dense city.

Sydney planners should take note, says the president of the Western Sydney Regional Organisation of Councils, Barry Calvert.

According to the Cooling Western Sydney study undertaken jointly by the University of New South Wales and Sydney Water, while greenery does have a cooling effect, the most effective results come from a combination of water-based technologies – these include fountains – and cool material technologies such as cool roofs and pavements.

The study used sophisticated modelling and expertise in microclimatic research to evaluate the impact of urban heat mitigation technologies (greenery, water and cool materials) in western Sydney.

It then modelled specific sites in western Sydney to assess the impact of specific technologies, including reducing energy costs and heat-related deaths, which are up to three times higher in western Sydney during extreme heat events.

The NSW government is currently planning the new Western Parkland City around the second airport at Badgerys Creek, 60km west of the CBD.

The Aerotropolis, now renamed Bradfield, will eventually be home to 1.5 million people, but with temperatures 6C to 10C higher than the coast, the region presents a challenge to ensure it does not become a heat island, with an unhealthy microclimate.

The emphasis so far has been on creating a tree canopy, though the early plans also aim to retain creeks and waterways and avoid building in flood plains.

The new study urges a focus on water infrastructure to enable greater cooling and the use of materials that have a high reflective (albedo) score.

That will require planning to ensure the reuse of water and measures such as banning black roofs and dark road surfaces.

The study used experimental data about the urban heat island effect from 101 Australian and Asian cities to understand how the phenomenon worked.

The study found that higher reductions in temperatures have been achieved by the scenario of water-based technologies combined with cool materials.

“More specifically, it was found that increasing the global albedo to 0.5 by the large scale application of cool materials and implementing water-based technologies may result in an average air temperature reduction of 1.5C in the area, with local reductions close to the water reaching 10C,” the study said.


Based on data from the summer of 2016-17, when there were severe hot spells, the modelling showed that combined use of cool materials and water could lower the cumulative heat-related deaths in the far west from 14 to approximately 7.5 deaths per 100,000 inhabitants.

Closer to the coast, heat-related deaths could be lowered to approximately five deaths per 100,000 inhabitants.

“While greenery does have a cooling effect, the study shows the most effective urban heat mitigation technologies are those incorporating a combination of water-based technologies with cool materials,” the study found.

Calvert said investments in water supply services and infrastructure could help cities become more resilient to global warming and heatwaves.

“This could consist of such things as installing or repairing fountains for drinking and cooling, and for cooling spaces by using water spray fountains, along with cooling by wetting streets,” he said.

“Fountains can decrease surrounding air temperatures by 3C and their cooling effect can be felt up to 35 metres away,” Calvert said.

“Fountains also have social value. Children play in fountains and people enjoy fountains in parks and squares, and they serve as meeting places.

“Who knows? Maybe it’s time we turned greater Sydney into a city of fountains?” Calvert said.

They key facts in the article:

• Fountains can reduce air temperature by 3 degrees C (5.4 F)
• Their cooling effect can be felt up to 35 metres (115 feet) away
• A combination of cool materials and fountains can reduce temperatures over large areas by 1.5 C, and smaller areas by 10 C

If we combined fountains *and* trees *and* pale roofs, we might almost eliminate the urban heat island effect.   I wrote a piece where researchers said that a street lined with large trees could cut temperatures by 5 degrees C compared to adjacent areas without trees---see "The Magic of Trees".

Your city can choose to change

 From a tweet by Brent Toderian, town planner

Amsterdam wasn’t always like it is today. In the 50s-60s they surrendered to cars too. But starting in the ‘70s, they chose to change. And they kept choosing to change for decades. They’re STILL choosing to change, as @schlijper’s great pics show.

Your city can choose to change.

[Large deliveries are made by small electric vans; note the beautiful trees] 

Mind blowing potential

From The Guardian:

Planting billions of trees across the world is by far the biggest and cheapest way to tackle the climate crisis, according to scientists, who have made the first calculation of how many more trees could be planted without encroaching on crop land or urban areas.

As trees grow, they absorb and store the carbon dioxide emissions that are driving global heating. New research estimates that a worldwide planting programme could remove two-thirds of all the emissions that have been pumped into the atmosphere by human activities, a figure the scientists describe as “mind-blowing”.

The analysis found there are 1.7bn hectares of treeless land on which 1.2tn native tree saplings would naturally grow. That area is about 11% of all land and equivalent to the size of the US and China combined. Tropical areas could have 100% tree cover, while others would be more sparsely covered, meaning that on average about half the area would be under tree canopy.

The scientists specifically excluded all fields used to grow crops and urban areas from their analysis. But they did include grazing land, on which the researchers say a few trees can also benefit sheep and cattle.

“This new quantitative evaluation shows [forest] restoration isn’t just one of our climate change solutions, it is overwhelmingly the top one,” said Prof Tom Crowther at the Swiss university ETH Zürich, who led the research. “What blows my mind is the scale. I thought restoration would be in the top 10, but it is overwhelmingly more powerful than all of the other climate change solutions proposed.”

Crowther emphasised that it remains vital to reverse the current trends of rising greenhouse gas emissions from fossil fuel burning and forest destruction, and bring them down to zero. He said this is needed to stop the climate crisis becoming even worse and because the forest restoration envisaged would take 50-100 years to have its full effect of removing 200bn tonnes of carbon.

But tree planting is “a climate change solution that doesn’t require President Trump to immediately start believing in climate change, or scientists to come up with technological solutions to draw carbon dioxide out of the atmosphere”, Crowther said. “It is available now, it is the cheapest one possible and every one of us can get involved.” Individuals could make a tangible impact by growing trees themselves, donating to forest restoration organisations and avoiding irresponsible companies, he added.

Other scientists agree that carbon will need to be removed from the atmosphere to avoid catastrophic climate impacts and have warned that technological solutions will not work on the vast scale needed.

Jean-François Bastin, also at ETH Zürich, said action was urgently required: “Governments must now factor [tree restoration] into their national strategies.”

The research is based on the measurement of the tree cover by hundreds of people in 80,000 high-resolution satellite images from Google Earth. Artificial intelligence computing then combined this data with 10 key soil, topography and climate factors to create a global map of where trees could grow.

This showed that about two-thirds of all land – 8.7bn ha – could support forest, and that 5.5bn ha already has trees. Of the 3.2bn ha of treeless land, 1.5bn ha is used for growing food, leaving 1.7bn of potential forest land in areas that were previously degraded or sparsely vegetated.

[Read more here]

My comments:

1. Note how little of the maps are green.  Only a small proportion of land reforested is needed to remove 2/3rds of the CO₂ mankind has emitted in the last 150 years!
2. Crop land needn't be omitted.  The UK and Irish landscape, a mix of small copses and hedgerows as well as open fields hints at a pattern where the edges of fields (say 10% of the cropland) could be planted to forest
3. As I've mentioned before, the difficult part of reducing emissions to zero is the last 20%, which is agriculture.  Cutting emissions from power generation and transport will be easy.  As long as people want to eat meat (except vat-meat) agricultural emissions will be hard to cut.  But agriculture can still do its bit by planting 10 metre wide (the width of a two lane highway) strips around crop fields.  Although this will need to be subsidised, the cost will be tiny compared to the catastrophic costs of global heating.
4. I've talked about the benefit of an urban canopy here.  An urban canopy can reduce urban temperatures by 4 or 5 degrees C (6.4 to 7.5 degrees F).   Every street should be lined by a dense canopy of trees.  Every piece of spare municipal or state land should be forested.
5. In Australia, most of the native eucalypts are very flammable.  Given rising temperatures and increasing drought, we shouldn't plant inflammable species, because at the first bushfire, all their stored CO₂ will just be released back into the atmosphere.  Brisbane Box Gum isn't inflammable, nor is the Blackwood.  But here in Oz, and in southern California and Mediterranean, perhaps less flammable species like (most) oaks, beeches, birches, will be superior to eucalypts.
6. We can begin right now.  We don't have to wait for electricity generation to transition to 100% carbon-zero, which will take another 15 years.   We don't have to wait until 100% of transport is electric (or maybe, hydrogen-fuelled), which will take another 25 years.  
7. This report fills me with hope.  We can stop global heating.   A mixture of a rapid transition to a green electricity and transport system and of reforesting our landscape will do it.  And meanwhile, we can work on reducing emissions in air travel, iron & steel, cement production and agriculture.  It's doable and feasible, and will cost just a couple of percent of GDP. 

The global energy transformation is well underway

From IEEFA:

The global energy sector transformation is a technology‑driven disruption fueled by five compounding factors:

• The economics of renewables are working
• Global capital is fleeing coal
• Government policies are reinforcing the trend away from coal
• Leading corporates are pivoting away from coal
• China plans to dominate this new Industrial Revolution

The economics of renewables are working

The global energy transformation is being driven by the combination of accelerating technology innovation and economies of scale. This has led the cost of electricity generated by wind farms to drop by 50% this decade, while solar costs have declined by well over 80%.

Offshore wind is set to follow a similar deflationary cost trajectory. Lithium ion batteries have likewise dropped in cost by over 50% in the last three years, putting electric vehicles on a path to displace internal combustion engines this coming decade.

Solar costs are also dropping in the four largest electricity markets in the world. While solar costs have diminished 50% in the last four years in Japan, they are still well above grid parity. In contrast, both the U.S. and India saw renewable energy go below grid parity with thermal power in 2017. At the same time, China is on target to achieve grid parity by 2020. With continuing solar cost deflation of some 10% annually, these trends will continue.

Alternative energies are creating a wave of stranded fossil fuel assets. As a leading market for renewables, India is now grappling with some US$60bn of thermal power projects in financial distress, unable to compete with low-cost renewables and hence repay loans.

Global capital is fleeing coal

IEEFA has tracked the number of globally significant financial institutions that have introduced polices to restrict lending, insurance and investing in thermal coal mines and coal-fired power plants.

To date, 113 globally significant financial institutions are exiting coal. Of the top forty global banks, 45% now have coal lending prohibitions.

There is a new announcement occurring on average every week to date in 2019.

This capital flight from the coal sector is resulting in developments like Adani’s proposed Carmichael thermal coal mine in Queensland being unable to find external finance.

Government policies are reinforcing the trend away from coal

In 2015, India set a target to build 175 gigawatts (GW) of renewables by 2022. Three years later, the ambition was lifted to 500GW by 2030. Global capital is endorsing this new low-cost solution.

India is not alone. South Korea recently set a target to build 58GW of renewables by 2030, while Taiwan set a target of 27GW by 2025.

Earlier in 2019, Thailand introduced a new energy plan to 2037, and coal’s market share target was halved to just 12%. That Thailand is also jumping onto the renewables bandwagon is not what the coal industry was expecting.

Increasingly, the low cost of renewables is making more ambitious targets a sensible economic proposition.

Leading corporates are pivoting away from coal

In May 2019, BHP announced it would no longer invest in thermal coal. The technology landscape had moved on, and the need to decarbonise to achieve the Paris Agreement means BHP sees thermal coal as increasingly obsolete.

RIO Tinto completed its global exit from coal in 2018, having taken advantage of buyer interest to exit without significant losses since 2014.

Australia’s leading industrial conglomerate announced acquisition plans in both lithium and rare earths in May 2019, both key inputs into low carbon emission industries. It is no coincidence that Wesfarmers also completed its exit from coal mining in 2018.

China plans to dominate this new Industrial Revolution

China installed 45-50% of all solar globally in both 2017 and 2018. It accounted for half of all electric vehicle sales globally in 2018 and is the world’s largest miner and processor of lithium and rare earths.

China is on a clear path towards decarbonisation and is a world leader in zero emission technologies of the future.

In May 2019, China’s National Development and Reform Commission announced a tender for 21GW of renewable energy, an investment program of US$25bn. This is the largest renewable energy investment in global history, and there is no subsidy support.

With this, China will reach its target of grid parity for both wind and solar by 2020.

[Read more here]


Right-wing denialists have little in common with logic and common-sense, so these facts won't change their dotty opposition to the renewables revolution.  But the denialists are increasingly isolated and ignored.  They will try to prop up fossil fuels with even more subsidies, but this will fail.  I believe there won't be many coal power stations operating in 2030, 90%+ of world car and truck sales will be electric by 2030, and serious steps will have been taken to reduce emissions from burning and clearing forests and from agriculture.  The politics have shifted irreversibly—Greta Thunberg has ensured that.

Will we be in time?  Global temperatures are rising by 0.2 degrees C every decade.  But the transformation taking place will ensure that by 2040, emissions will have halved.  This is a compound rate of decline of 3.2% per annum, which isn't fast enough.  However, at that rate of decline, we will have cut emissions by 75% by 2040, and by 90% by 2060.  So global temperatures will rise by another 0.6 degrees, which is still less than 2 degrees from the second half of the 19th century.  In the meantime, by planting an urban tree canopy and changing agriculture practices, we could remove CO₂ from the atmosphere.

The denialists have shifted their argument from saying "it's not happening" to "it's not us" to "it's too late".  It's not.

The magic of trees

Plane trees in Green Park, London.
Source: The Royal Parks

Tree-lined street in Tulsa
Source: Strong Towns.

From ZME Science:

The fact that cities are heat islands has been thoroughly documented in recent years — in all parts of the world, urban areas are considerably hotter than their surroundings. However, trees can help counterbalance that phenomenon, helping to keep our cities cooler. The effect is especially pronounced for a large number of trees.

The list of benefits that trees provide in urban areas is huge. Not only do they help absorb carbon and pollutants from the air, but they help with soil erosion and stability, water absorption and filtration, they provide ecosystems for a number of creatures, and offer shade and protection from wind. Studies have shown that trees inspire children to be more curious and fond of nature, increase property values, and can even help reduce criminality rates.

Another service which trees provide is thermal regulation. That has been suggested by previous studies and is quite intuitive. However, a new study shows that the relationship isn’t linear. When the canopy cover reaches a particular threshold, the effect is much more pronounced.

“We found that to get the most cooling, you have to have about 40 per cent canopy cover, and this was strongest around the scale of a city block,” says Carly Ziter, an assistant professor of biology in the Faculty of Arts and Science, and lead author of the study. “So if your neighbourhood has less than 40 per cent canopy cover, you’ll get a little bit of cooling, but not very much. Once you tip over that threshold, you really see large increases in how much you can cool areas off.”

The effects can be huge. The temperature difference from tree-less area just a few hundred meters away from an area with a heavy canopy cover can be as high as four or five degrees Celsius. It’s not just the shade either. Trees transpire, giving off water vapor, almost like a natural air conditioner.

[Read more here]

There is much you can do, personally, to stop global warming.  You can become a vegetarian; you could put solar panels on your roof; you could get an electric car.  And you can plant trees on your own property, while also persuading your local council to plant trees as well, along streets, next to streets, and next to municipal buildings.