Tag Archives: population

Planetary Emergency

Global energy budget from Trenberth et al 2009

This week’s lecture in my thermodynamics course for first-year undergraduate students was about thermodynamic systems and the energy flows in and out of them. I concluded the lecture by talking about our planet as a thermodynamic system using the classic schematic in the thumbnail [see ‘Ample sufficiency of solar energy‘ on October 25th, 2017 for more discussion on this schematic].  This is usually a popular lecture but this year it had particular resonance because of the widely publicised strikes by students for action on climate change.  I have called before for individuals to take responsibility given the intransigence of governments [see ‘Are we all free riders‘ on June 6th, 2016 or ‘New Year Resolution‘ on December 31st, 2014]; so, it is good to see young people making their views and feelings known.

Weather-related events, such as widespread flooding and fires, are reported so frequently in the media that perhaps we have started to ignore them as portents of climate change.  For me, three headlines events have reinforced the gravity of the situation:

  1. The publication earlier this month of a joint report by UNICEF and the Royal College of Paediatrics and Child Health that air pollution in the UK so high that it is infringing the fundamental rights of children to grow up in a clean and safe environment; and, under the Government’s current plans, air pollution in the UK is expected to remain at dangerous levels for at least another 10 years.
  2. The warning earlier this month from the Meteorological Office in London that global warming could exceed 1.5C above pre-industrial levels within five years.  In my lecture, I highlighted that a 2C rise would be equal to the temperature 3 million years ago when sea levels were 25 to 35m high; and, a 1m rise in sea level would displace 145 million people globally [according to Blockstein & Weigmann, 2010].
  3. The suspension of construction of the new nuclear power station on Anglesey by Hitachi, which leaves the UK Government’s energy strategy in disarray with only one of the six planned new power stations under construction.  This leaves the UK unable to switch from fossil-fuelled to electric vehicles and dependent on fossil fuel to meet current electricity demand.

I apologise for my UK focus this week but whereever you are reading this blog you could probably find similar headlines in your region.  For instance, the 2016 UNICEF report states that one in seven children worldwide live in toxic air and air pollution is a major contributing factor in the deaths of around 600,000 children under five every year.  These three headlines illustrate that there is a planetary emergency because climate change is rapidly and radically altering the ecosystem with likely dire consequences for all living things; that despite a near-existential threat to the next generation as a consequence of air pollution most governments are effectively doing nothing; and that in the UK we are locked into a fossil-fuel dependency for the foreseeable future due to a lack of competent planning and commitment from the government which will compound the air pollution and climate change problems.

Our politicians need to stop arguing about borders and starting worrying about the whole planet.  We are all in this together and no man-made border will protect us from the impact of making the planet a hostile environment for life.

Ample sufficiency of solar energy?

Global energy budget from Trenberth et al 2009

I have written several times about whether or not the Earth is a closed system [see for example: ‘Is Earth a closed system? Does it matter‘ on December 10th, 2014] & ‘Revisiting closed systems in Nature‘ on October 5th, 2016).  The Earth is not a closed thermodynamic system because there is energy transfer between the Earth and its surroundings as illustrated by the schematic diagram. Although, the total incoming solar radiation (341 Watts/sq. metre (W/m²)) is balanced by the sum of the reflected solar radiation (102 W/m²) and the outgoing longwave radiation (239 W/m²); so, there appears to be no net inflow or outflow of energy.  To put these values into perspective, the world energy use per capita in 2014 was 1919 kilograms oil equivalent, or 2550 Watts (according to World Bank data); hence, in crude terms we each require 16 m² of the Earth’s surface to generate our energy needs from the solar energy reaching the ground (161 W/m²), assuming that we have 100% efficient solar cells available. That’s a big assumption because the best efficiencies achieved in research labs are around 48% and for production solar cells it’s about 26%.

There are 7.6 billion of us, so at 16 m² each, we need  120,000 square kilometres of 100% efficient solar cells – that’s about the land area of Greece, or about 500,000 square kilometres with current solar cells, which is equivalent to the land area of Spain.  I picked these countries because, compared to Liverpool, the sun always shines there; but of course it doesn’t, and we would need more than this half million square kilometres of solar cells distributed around the world to allow the hours of darkness and cloudy days.

At the moment, China has the most generating capacity from photovoltaic (PV) cells at 78.07 GigaWatts or about 25% of global PV capacity and Germany is leading in terms of per capita generating capacity at 511 Watts per capita, or 7% of their electricity demand.  Photovoltaic cells have their own ecological footprint in terms of the energy and material required for their production but this is considerably lower than most of our current sources of energy [see, for example Emissions from photovoltaic life cycles by Fthenakis et al, 2008].


Trenberth KE, Fasullo JT & Kiehl J, Earth’s global energy budget, Bulletin of  the American Meteorological Society, March 2009, 311-324, https://doi.org/10.1175/2008BAMS2634.1.

World Bank Databank: https://data.worldbank.org/indicator/EG.USE.PCAP.KG.OE

Nield D, Scientists have broken the efficiency record for mass-produced solar panels, Science Alert, 24th March 2017.

2016 Snapshot of Global Photovoltaic Markets, International Energy Agency Report IEA PVPS T1-31:2017.

Fthenakis VM, Kim HC & Alsema E, Emissions from photovoltaic life cycles, Environmental Science Technology, 42:2168-2174, 2008.

Airborne urban mobility

Pop.Up_copyright Italdesign 2

At the Airbus PhD workshop that I attended a couple of weeks ago [see my post entitled Making Engineering Work for Society on September 13th 2017], Axel Flaig, Head of Airbus Research and Technology, gave us an excellent opening presentation describing their vision for the future.  Besides their vision for the next generation of passenger aircraft with reductions in CO2, NOx and noise emissions of 75%, 90% and 65% respectively against 2000 levels by 2050, they are also looking at urban air mobility.  We have 55 megacities [cities with a population of more than 10 million] and it is expected that this will increase to 93 by 2035 [see my post entitled ‘Hurrying Feet in Crowded Camps’ on August 16th, 2017].  These megacities are characterized by congestion and time-wasted moving around them; so, Airbus is working on designs for intra-city transport that takes us off the roads and into the air.  Perhaps the most exciting is the electric Pop.up concept that is being developed with Italdesign.  But, Airbus are beyond concepts: they have a demonstrator single-seater, self-pilot vehicle, the Vahana that will fly in 2017 and a multi-passenger demonstrator scheduled to fly in 2018.

Soon, we will have to look left, right and up before we cross the road, or maybe nobody will walk anywhere – though that would be bad news for creative thinking [see my post on ‘Gone Walking’ on 19th April 2017], amongst other things!


Image from http://www.airbus.com/newsroom/press-releases/en/2017/03/ITALDESIGN-AND-AIRBUS-UNVEIL-POPUP.html where there is also a video.

Hurrying feet in crowded camps

Five years ago I wrote about the potential ‘Population Crunch‘ [September 15th, 2012] that could lead to a large increase in the size and number of cities – perhaps upto 1500 new cities emerging over the next few decades as the global population rises from 7.6 billion to 9.8 billion by 2050 [see UN revised report, 2017].  It is a significant challenge to provide an acceptable quality of life to the citizens of these new cities as well as existing ones.  People have been concerned about the density of population in cities and its impact on individuals for more than a century.  In 1910, W.H. Hudson in ‘A Shepherd’s Life’ [Penguin Books, 1910] wrote, somewhat tongue-in-cheek, about London: ‘Some over-populated planet in our system discovered a way to relieve itself by discharging its superfluous millions on our globe – a pale people with hurrying feet and eager, restless minds, who live apart in monstrous, crowded camps, like wood ants that go not out to forage for themselves’  Nothing seems to have changed!