Not Black and White: The Complications of White Roofs

Source: Jaun Carlos PE

After talking about green roofs, I was excited to laud the advantages of white roofs. They increase the albedo of the roofs allowing sunlight to bounce off of them. Which in turn keeps homes and cities cooler, so less energy is spent running the air conditioning. Unlike green roofs, they can be a cheap renovation for any building. (That's US$151 savings during installation for ever square meter!) Pack up shop, we solved the crisis with a few cans of paint!

I should have known that it might be too good to be true. A Stanford study looked at the global effects of a world filled with white roofs and found that the price for a locally cooled city was an increase in total global temperature. Their model predicted a .02^oC decrease in temperature around areas with white roofs but an increase of .07^oC worldwide. Part of the problem is soot and other air pollutants, heated from above and below, causing extra warming.

A study of the economic costs and benefits of environmental roofing found that white roof more economical for global cooling.  However, this was based on CO₂ offset by saving energy and relief of the urban heat island. Since there was no mention of the global heating caused by increased white roof, I tend to be a little skeptical.

Even if the white roof didn't warm the planet on a global scale, there are some areas where they would still not be worthwhile on the local scale. Cities with cooler climates may find that the savings from cooling in the summer are not offset by the additional heating in the winter. 

I wish I could say that a white roof is a great substitution if you can't have a green roof. However based on my reading, I'm afraid that running blindly into adapting white roofs may backfire. So for now, if it's not easy being green consider being solar. Perhaps absorbing light and using it as clean energy is better than reflection.

The Shire of London: The Benefits of Green Roofs

Source: Hobbiton Movie Set Tours

While they may invoke images of Hobbits and the Shire, green roofs could be part of the solution to keeping cool in a warming world. The urban heat island effect (urban areas becoming warmer than surrounds due to more pavement) can raise the temperature in the city by 12^oC at night and currently affects 54% of the world's population.


Source: Marilyn Novy

The reflectivity (albedo) and latent cooling are what draw people to green roofs, but much of their temperature regulation comes from insulation (Del Barrio, 1998). They are most cost effective for old uninsulated buildings, which make up 50% of the UK's homes and businesses. This reduction in energy for heating and cooling will help mitigate CO₂ emissions.

People may argue against this initiative because of the expense (10-14% more for a 60-year roof). However green roofs provide benefits that plain old insulation does not offer. They reduce runoff, cool the outdoor temperature (especially when paired with green walls between close buildings), capture pollutants (notably ozone ), and create easy access to nature. This seems like a lovely way to combine adaptation with an improved lifestyle.

Things Are Going to Get Extreme

When thinking about climate adaptation, it's hard to figure out exactly where to start. The Intergovernmental Panel on Climate Change (IPCC) said we could expect an increase of:

Source: The Washington Sun

• milder cold days
• warmer hot days
• heat waves
• heavy precipitation
• droughts
• intense cyclones
• high sea levels

I've seen a lot of this on the news. And whenever one of these events occurs I am reminded that climate change brings the threat of similar events. But what really scared me during my research, my 'oh wow' moment, was looking at these 4 squiggly graphs.



PR (probability ratio): P1/ P0 where P1 is the probality of an event happening
after a given global mean warming  and P0 is the probability of it happening
before the industrial revolution.

FAR (fraction of attributable risk): 1-PR which yield the amount that humans
contributed to the probability of a set of events occurring

Blue: Daily weather that had a 1 in 100 chance of happening before the industrial revolution

Red:  Daily weather that had a 1 in 1000 chance of happening before the industrial revolution

Source: Fischer, Knutti, 2015

These graphs are the predictions of 25 different models and show the expected trends for heavy precipitation (a & c) and extreme heat (b&d). For both heat and precipitation, the more unusual the event the more its frequency will increase. These same events will probably be, in part, due to human activity. (Fischer, Knutti, 2015) Knowing the resulting death and distruction from extreme events, society needs to take a long hard look in the mirror. The scale of the temperature increase and our respective blame dwarfs the increase for heavy precipitation, which was not what I expected growing up on the East Coast of the US.

Looking at these graphs, knowing that we are currently at .85^oC global increase, the international goal of 2^oC seems recklessly high. And seeing how the current COP21 pledges would result in a 2.7^oC increase, adaptation need to be swift. Therefore, I plan on first looking at preparations for higher temperatures and droughts.

Practicing What I Preach

I decided to figure out my own carbon footprint. After looking through a few online calculators, I opted for Carbon Independent. It was comprehensive and transparent with a simple design. I loved how it broke down each item in terms of CO₂ used. It also took into account the CO₂ that public institutions, such as my university, release on my behalf. After quickly filling in the form based on my time in London since September, I hit 'View/Print Summary' and...




Source: Carbon Independent

 

Yikes! One year in London, living my current lifestyle, would lead to 9.04 tonnes of CO₂ released into the atmosphere.

Unfortunately, I live in university housing, so improving the sustainability of my home will be difficult. Instead I must *gulp* change my lifestyle. I will be updating my progress in a month, and we'll see how I am living up to the new standards.

In the meantime, what's your CO₂ emissions?

Preventing the Worst

TED: Climate change is happening. Here's how we adapt.

Source: ted.com

Upon first watching Alice Bows-Larkin's TED talk I walked away with three primary thoughts.

1. A 4°C change in the atmosphere is scary. With infrastructure not being able to handle the new strain, corn and wheat yields down 40%, rice yields down 30%, and the pure discomfort of effectively adding 10°C to the hottest days, Hollywood has no excuse for poor source material in their disaster films.
2. "Wow, I haven't heard anyone say that we can actually keep temperature change below 2°C globally in long time." Alice Bows-Larkin's cure was for the wealthiest citizens and nations (e.g. anyone able to read this blog) should reduce their CO₂ emission by 10% per year. A task that seems challenging but sustainable.
3. The cynical idea that politicians and businesses will never allow the pause on economic growth for "planned austerity".

The amount each country has contributed to climate change
based on their CO₂, methane, nitrous oxide, and
aerosol emissions per billion people.
Source: Mathews, et al., 2014

Climate-Demographic Vulnerability Index based on predicted
climate variability and population growth. The higher numbers
translate to higher vulnerability. Source: Samson, et al.,2011

The paper Alice Bows-Larkins collaborated on and quoted also mentioned an approach forward which I think is promising, "Mitigate for 2°C but Adapt for 4°C". This would involve policies to attempt to curb CO₂ emissions and keep global temperature change below 2°C while preparing infrastructure for 4°C. I believe that this global goal of 2°C temperature change, historically used when regulating emissions, will prevent delays in political system caused by debating new standards. The preparation aspect will allow vulnerable developing nations, who's contribution climate change is minimal, to get support from wealthier nations. 

The paper mentions that assigning accountability may strain international relations. However, for the sake of human rights, I believe that any legal foothold given to the most vulnerable citizens is worthwhile. Another concern the paper mentioned is the possibility of preparations negating any reduction in emissions. I agree, this cannot be allowed to happen. However, this warning calls for innovation not despair.

I am on the 'aim for 2°C and prepare for 4°C' bandwagon. Therefore, I will attempt to reduce my carbon footprint by 10% while posting the adaptions that will help prepare for the worst.