Tag Archives: carbon emissions

Difficult or inconvenient data about electric vehicles

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photograph of a MDI Airpod 2.0The embodied carbon (i.e. the greenhouse gas emissions produced by its manufacture and assembly) of a typical small (compact) battery electric vehicle (BEV) is about 14 tonnes CO2 compared to about 7 tonnes CO2 in a compact internal combustion engine vehicle (ICEV) [see brusselblog.co.uk for overview of estimates from several sources].  This is mainly a result of the embodied carbon in the batteries.  My compact ICEV does about 50 mpg and we drive about 8,000 per year so we burn 160 gallons per year and one gallon generates about 9 kg CO2; thus, the carbon emissions from my ICEV are about 1.4 tonnes CO2/year. Hence, with our driving habits, building and using a compact ICEV car for five years is equivalent, in carbon emissions (= 7 + (1.4 x 5)), to just building a small electric car.  This does not account for the carbon footprint of electricity generation for the electric car which will not be zero and be dependent on how the electricity is generated; nor is recycling of your old vehicle included.  If you already have a ICEV car then your additional emissions resulting from its continued use will take about a decade to be more than buying a new electric car though by buying an electric vehicle you will move the pollution away from where you live and work.  If you buy an electric SUV, as about 45% of new car purchasers do worldwide [see IEA data], then many more years will be required to acheive a net reduction in carbon emission because the embodied carbon in an electric SUV can be five to ten times more than a compact ICEV.  The challenge for engineers is to develop vehicles that have both zero emissions in use and also zero embodied carbon.  Meanwhile, the bottom line is to use public transport whenever possible but if you need a car then have a small one and keep an electric one for much longer than an internal combustion engine vehicle – neither helps achieve net zero.

Image: the MDI Airpod that runs on compressed air [see ‘Hot air is good for balloons but cold air is better for cars‘ on May 19th , 2021.

Is it time to change priorities on climate change?

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It seems unlikely that global warming will be limited to only 1.5 degrees Centigrade above pre-industrial levels in the light of recent trends in temperature data [see ‘It was hot in June and its getting hotter’ on July 12th, 2023 ]. It is probable global warming will lead to average surface temperatures on the planet rising by 4 or 5 degrees, perhaps within a matter of decades.  A global average temperature rise of only 2 degrees would make the Earth as warm as it was 3 million years ago when sea levels were 25 to 35 m (80 to 130 ft) high (Blockstein & Wiegman, 2010).  While it is still important to aim for zero carbon emissions in order to limit global warming and avoid global temperatures reaching a tipping point, it seems improbable that politicians worldwide will be able to agree and implement effective actions to achieve the goal in part because of the massive, vested interests in industrialised economies based on fossil fuels [see ‘Are we all free-riders?’ On April 6th, 2016].  Hence, we need to start planning for potentially existential changes in the climate and environment that will force us to adapt the way we live and work.  In addition to rises in sea levels, a world that is 4 degrees hotter is likely to have an equatorial belt with high humidity causing heat stress across tropical regions that make them uninhabitable for most of the year. To the north and south of this equatorial belt will be mid-latitude belts of inhospitable deserts extending as far north as a line through Liverpool, Manchester, Hamburg, the straits north of Sapporo in Japan, Prince Rupert in British Columbia and Waskaganish on the Hudson Bay.  The habitable zones for humans are likely to be north of this line and in the south in Antarctica, Patagonia, Tasmania and the south island of New Zealand.  Agriculture will probably be viable in these polar regions but will compete with a very dense population [see ‘Belts of habitability in a 4° world’ in Nomad Century by Gaia Vince].  In other words, there will likely be mass migrations that will force a re-organisation of society and a restructuring of our economies.  Some estimates suggest that there could be as many as 1.2 billion environmental migrants by 2050 (Bellizzi et al, 2023).  We need to start adapting now, the world around us is already adapting [see ‘Collaboration and competition’ on June 8th, 2022].

It was hot in June and its getting hotter

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Decorative image of a summer flowerLast month was the first June on record when the daily average global 2-metre surface temperature exceeded 1.5 °C above pre-industrial levels [1] and last week, on July 6th, the daily global air temperature hit a record high of 17.23 °C [2]  In 2020 it was estimated that the world’s remaining carbon budget was about 500 gigatonnes CO2 if there was to be a 50% chance of limiting global warming to 1.5 °C. It is now estimated that the remaining budget is about 250 gigatonnes CO2, i.e., it has halved in three years, as a result of continued pollution and temperatures rising faster than expected [3].  At the current rate of emissions, this budget will be exhausted in about six years.  Hence, it seems very likely that global temperatures will rise by more than 1.5 °C and perhaps by as much as 4 °C this century.  The last time the Earth was that hot was about 15 million years ago during the Miocene when sea levels were 40 m higher [4].  It is time to get much more serious about reducing carbon emissions instead of just talking about it.  Current targets for reducing emissions are so far in the future that they are beyond the horizon – effectively out of sight and out of mind.  We need to be costing everything in terms of carbon emissions and making decisions that reduce emissions now.

[1] Climate graphic of the week: first days of June bring record heat, FT June 17, 2023.

[2] Global temperature hits record high, FT Weekend 8th July 2023 based on data from NOAA.

[3] Forster PM, Smith CJ, Walsh T, Lamb WF, Lamboll R, Hauser M, Ribes A, Rosen D, Gillett N, Palmer MD, Rogelj J. Indicators of Global Climate Change 2022: annual update of large-scale indicators of the state of the climate system and human influence. Earth System Science Data. 15(6):2295-327, 2023.

[4] Foster GL, Rohling EJ. Relationship between sea level and climate forcing by CO2 on geological timescales. Proceedings of the National Academy of Sciences. 110(4):1209-14, 2013.

Conflicted about cost-benefit analysis of international conferences

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Decorative image of an aircraftLast week I wrote about my stimulating experience of attending a conference in Orlando, Florida and presenting our recent research to the experimental mechanics community for the first time in four years.  Whilst there, I was conscious of the ecological footprint of my trip – the venue was making extensive use of single use plastics on a scale that surprised me.  However, my trans-Atlantic flight had an order of magnitude larger impact.  It is difficult to find a reliable estimate of the carbon emissions for a return flight between the UK and Florida but 1,267 kg CO2 from the Guardian newspaper website lies between a lower bound estimate of 856 kg CO2 from iata.org and and an upper bound of 2,200 kg CO2 from myclimate.org.  This is equivalent to about one-sixth of my annual domestic carbon footprint of 9,000 kg CO2 using the calculator on the World Wildlife Fund website.  The UK average footprint is 9,300 kg CO2/capita and the global average is 6,300 kg CO2/capita.  The question is whether it is justifiable to generate additional emissions to attend a research conference?  The prime motivation of the research that I presented is to support the development of aircraft which are lighter with less embedded carbon and use less energy while also having a longer useful life.  Ultimately, supporting the aviation industry to achieve its target of zero-net emissions by 2050.  The carbon emissions of the global aviation industry in 2021 were 720 Mt CO2 [see IEA report]; hence, if my research contributes towards one hundredth of a percent reduction in these emissions then this would be 72,000 kg CO2/year.  It seems reasonable to cause a tenth of this annual saving each year (7,200 kg CO2/year) for the next ten years in order to deliver the required technology, i.e., committing one year’s savings to achieve an annual saving in perpetuity.  The problem is that I do not have a reliable estimate of the carbon footprint of my research activities.  I supervised an MSc student a couple of years ago who conducted a carbon audit of the School of Engineering and estimated the carbon emissions due to research alone to be 61,531 kg CO2 excluding heating, lighting and travel.  My group might be responsible for 10% of these emissions, i.e., about 6000 kg CO2; hence, adding about 1,200 kg CO2 to interact with other researchers at a conference seems reasonable and within a budget of 7,200 kg CO2. However, it is difficult to find reliable data to use in estimating carbon emissions for these activities and so perhaps the key conclusion is that we need more and better carbon audits to allow more informed decision-making.  In the meantime, perhaps attendence at an international conference once every four years is sufficient.

Image: Tayeb Mezahdia