* eats plants * loves science * scared of earthquakes * a bit opinionated *


Bjorn Lomborg economics

I’ve just seen a tweet of Bjorn Lomborg’s from the other day (yes, I’m a couple of days behind) on the cost of climate change versus the costs of mitigation. Here it is:

If you view his tweet on Twitter you will see that quite a few people have accused him of misrepresenting the report. For instance:


Is he making a false comparison? His 6% comes from this table in the Summary for policy makers:


Presumably he’s referring to the 2.1-6.2% reduction in consumption relative to a baseline in the row for 450ppm CO2eq. If so, then he’s chosen the upper value of the range which he tweets as being “Cost of policy higher than 6%”. This figure is also relative to a baseline, not annually. According to this IPCC presentation “this is equivalent to a reduction in consumption growth over the 21st century by about 0.06 (0.04-0.14) percentage points a year (relative to annualized consumption growth that is between 1.6% and 3% per year).”

Meanwhile, the IPCC WGII Summary for Policymakers puts the cost of climate change as:

With these recognized limitations, the incomplete estimates of global annual economic losses for additional temperature increases of ~2°C are between 0.2 and 2.0% of income (±1 standard deviation around the mean) (medium evidence, medium agreement). Losses are more likely than not to be greater, rather than smaller, than this range (limited evidence, high agreement).

On his Facebook page, Bjorn Lomborg says the 0.2-2% comes from a temperature rise of 2°C which we’ll reach sometime between 2055-2080. This seems to be consistent with the paragraph from the Summary for Policymakers above.

He’s comparing global economic losses annually with a reduction in consumption relative to a baseline. Is this a fair comparison?


How food labelling can make you fat

This is an interesting clip about how food labelling can influence our metabolism. The basic gist is: if you think you’ve eating something fattening, then you will think you’ve consumed more and this could affect digestion. By contrast, if you eat something labelled as low fat or fat free, you’ll feel like you’ve eaten less and so likely to eat more later.




Volunteering at British schools

I loved everything about the state-funded school my son attended for 6 months when we were in the UK and have written about the experience here. In most respects, I preferred the English school to the New Zealand school he attends now. I say most respects because there was one thing about the English school that was just *absurd*: the police checks required for parent volunteers who want to help out in the classroom.

I have always helped out in Daniel’s class just once a week for an hour or so since he started year 1 (he’s year 3 now). In New Zealand, anyone can volunteer and there’s no form to fill in and no police check to perform and no identification required. You simply negotiate a suitable time with the teacher, turn up and provide support for them. Daniel has always loved me doing this and I have found it useful knowing what they’re up to and his teachers have always been extremely grateful for the help.

When he started school in York, I volunteered my services again, only this time there was a form to fill in and a police check to undergo. This would have been fine except that identification was required. Unfortunately all I had with me was a New Zealand driver’s licence in my married name and an Australian passport in my maiden name (neither document was sufficient on its own). I stupidly didn’t take my marriage certificate or any other documentation with me to the UK. This meant that they could not confirm my identity. The school told me that they’d send the forms off to the police anyway but that I’d probably have to be fingerprinted. This was fine – especially since we had already been fingerprinted at Heathrow airport upon arrival – except that quite a few months passed before I heard back from the police and by the time I did, we only had a month left in York and so I decided it wasn’t worth it as there was still going to be a 4-6 week wait after my fingerprints were taken.

So I never got to volunteer at a State school in the UK which means that schools are turning away *free* help. I can understand why teachers and people who work with children should probably be police-checked, but a parent who is never alone with the children? I think this is ridiculous.


The consequences of climate change

The science journalist, Peter Hadfield (aka Potholer), has a great new youtube video about the consequences of climate change (in our lifetimes). I have to give credit to Moth from New Anthropocene for bringing it to my attention. This to me is good science communication: it’s simple, clear and interesting.


Here’s a quote from the very end which strikes a chord for me:

I’m not alarmed by a problem that our intelligence will allow us to mitigate; I’m alarmed at our ignorance and gullibility that leads us to wilfully ignore it.


The impact of climate change on human health

Chapter 11 of the IPCC report (yes, I’ve skipped a few chapters since my last post on this topic) is about Human health: impacts, adaptation and co-benefits. This is all about us so I think it deserves a post all on its own.

Climate change will affect human health in three ways:

  1. Weather: Directly through higher temperatures, heat waves, floods, droughts and fires.
  2. Natural systems: Environmental changes such as the contamination of freshwater resources and the spread of mosquitoes and ticks that carry diseases like malaria.
  3. Human systems: Impacts arising from climate-change induced crop failures which lead to undernutrition and mental illness; violent conflict arising from human migration and economic losses caused by inability to work due to high temperatures (heat exhaustion).


The health impacts of climate change do not increase linearly with temperature. A 4°C increase in temperature does not equate to double the impact when compared to an increase in 2°C; it will be more than double. Part of the reason for this is that the latitudes where people will benefit from less cold, the far north of the Northern Hemisphere, are less populous than the areas expected to suffer the most with extreme heat.

However, It’s not just the temperature that is important but also temperature variability – there’s evidence that deaths from heat waves are more likely early in the season before people have had a chance to acclimatise – and so winter mortality may not decrease in a warmer climate that is also more variable. What is clear though, is that the negative heath impacts of a hotter climate will outweigh any benefits from fewer cold-related health impacts.

The human body has limits to what it can tolerate temperature-wise. Body temperatures above 38°C lead to heat exhaustion and cognitive impairment. Body temperatures above 40.6°C lead to heat stroke, with risks of organ damage and loss of consciousness. The human body cannot tolerate wet bulb (100% humidity) temperatures above 35°C for long. If temperatures were to rise by 7°C, parts of the earth would become uninhabitable to humans as our bodies would not be able to dissipate metabolic heat. If the temperature were to rise by 11-12°C, most areas occupied by humans today would become uninhabitable. These are conservative estimates.

Hot days are particularly risky for those who work outdoors. They also lower economic productivity as those people will need breaks to avoid heat stress. Crop failures will lead to undernutrition and stunting in children and food insecurity. If populations are forced to migrate as a result of disasters or food insecurity then there’s a risk of violent conflict. There’s also evidence of a link between drought and psychological distress.

The frequency of floods is expected to increase with climate change and the populations most at risk are those in Asia, Africa, Central and South America.  The impact on human health is through drowning, injuries, hypothermia and the spread of infectious diseases. But there is also a psychological impact: anxiety and depression. There’s also expected to be an increase in intense tropical cyclones later this century.

More people are projected to be at risk of malaria because of climate change even when disease control efforts are factored in. There are no projections that it will spread to Europe or North America but once upon a time it was prevalent in these regions. The geographic area suitable for dengue fever is expected to increase with climate change as well. There may be regions which see improvements as some mosquitoes cannot tolerate temperatures above 40°C.

There’s lots that can be done to reduce the impact of climate change on human populations. These adaptive measures include improvements in public heath services, identifying at-risk populations, implementing early warning systems for things like heat waves and malaria outbreaks. Local interventions are also useful like increasing urban green spaces to counter the heat island effect.

The burden of climate change will fall heaviest on the world’s poor and will exacerbate diseases already in existence. The best adaptation strategy for these areas in the near term is to improve health services to these places to alleviate diseases already in place. Improving access to clean water, sanitation and taking steps to lift people out of poverty are other important adaptation strategies. But these strategies have their limits. Under business as usual, some of these places could see temperatures by the end of the century which for parts of the year are too high for the human body to tolerate work outdoors and this will have implications for the economy and productivity as well as health.

Human populations will benefit from some greenhouse gas reduction strategies. These are referred to as co-benefits and include things like reducing harmful pollutants from coal-fired power plants and solid fuel stoves which cause respiratory illness, lung cancer and cardio- and cerebrovascular disease; increasing access to contraception; eating less meat (which may reduce ischemic heart disease and some cancers); encouraging more active transport alternatives like walking and cycling; increasing urban green spaces.

Some populations will benefit. For instance, people living in temperate zones may see improvements in agricultural productivity, at least initially. But for the world as a whole, the impact will be negative particularly as time goes on.


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