sue mcnab

Climate change course blog

Leave a comment

Climate Change course – week 6

Impacts on Human Systems

Human Health & the Built Environment

Urban Heat Islands: temperature in cities higher than rural areas. This is due to proximity of tall buildings, reduced air circulation, drainage reducing evaporation, paved surfaces, removal of vegetation limiting plant transpiration (plants use solar energy during photosynthesis & respire water which cools the air), dark infrastructure such as black roofs etc which absorb heat, & heat generated by vehicles, factories & homes.  The larger the city and the more densely packed the buildings, the larger the heat island effect.  Cities in forest regions have a higher heat island than those surrounded by farmland or desert.

Goddard Space Flight Centre researchers use data collected by satellites to show how land surface temperature correlates to land development in cities around the US.

Heat islands cause power usage to surge (air conditioning etc) but also increase mortality of the elderly & those with respiratory & cardio-vascular illnesses.  Risk is at night when the body needs to cool down after heating during the day.  The cooling effect of evaporation at night is absent in cities & this can be exacerbated by air conditioning due to the heat expelled into the streets through their use.

How can cities be better designed to mitigate this?  More trees & parks interspersed throughout compact urban cores, painting road & building surfaces white instead of black, planting green roofs – complex problem & each city will have its own solution.

Climate change & food security

Rapidly growing world population.  86% will be living in less economically developed countries.  40% of land used to grow 3 main food staples – wheat, maize & rice. Rice most important of these – main food source for 50% world’s population.  Potatoes also increasingly important.  Need a secure food supply – needs to double in size by 2050.  Food supply security under threat, climate change being one of the factors.  Not just water shortages but also crop disease.  New ones emerging, & because of warming world, crops & their distribution moving to higher latitudes, polewards.  Since 1960’s “green revolution” due to fertilisers, herbicides, pesticides & fungicides, & also to greater farm mechanisation & intensification.  Large monocultures put food supply security at greater risk from pests & pathogens.  Spread of pathogens through crops has devastating effect on human populations.  Most serious is fungi – maize, wheat & rice threatened by 3 particular fungi & the loss of crops caused by these costs US$60billion pa.  A concerted attack by these fungi could result in us only being able to feed 38% of the world’s current population.  Pathogens on the move to new geographical areas threatening new crop species.  Fungi moving polewards 7km pa.

Tackling food security

Like a majority of the comments below, educate people to eat less, eat better (& especially less meat) & stop wasting food. Educate governments to take on the food industry. I also liked the earlier post (sorry-can’t remember whose) linking to – an interesting way to produce food. Final thought – if we all went on the 5:2 diet, think how much healthier we’d all be, how much better off we’d be financially (buying less food & not wasting it on diets & health fads that don’t work) & how much food we’d save… Lots of other good suggestions below so I won’t repeat them.

Reflections on week 6:

Another interesting week.  important themes: heat islands & the need to rethink our cities – remember that ridiculous building in London last summer! (; pathogens affecting food crops (I’d always thought that water supply was the main concern).  Most interesting: looking through people’s comments – good to know there are so many like-minds out there because you can start to feel you’re in a minority of one sometimes!


Leave a comment

Climate Change course – week 5

Ocean acidification has enormous implications for the functioning of natural systems. However, its human impact cannot be overlooked either. Will marine organisms be able to adapt to ocean acidification given the time scale for the predicted changes?  Increased carbon dioxide in the atmosphere is likely to lead to sea level rise. Are rising sea levels more of a threat to humanity than ocean acidification?

The timescales don’t seem long enough for those tiny intricate creatures to evolve a whole new protection mechanism. Not only will there be a tragic loss of species & habitat, but the food chain will be severely affected. Humans currently depending on fish for a living &/or food source will be forced to move, adding to the migration caused by the other danger of rising sea levels. In the UK we are currently witnessing the problems created by storms & flooding – the affect on communities, farming, power supplies, transport, & seeing the blame game that starts up between politicians, media & public. Imagine what this would be like if things really got serious – total chaos! This should be a massive wake-up call – we mustn’t do what we normally do which is to wait for the **** to really hit the fan – by then it will be much too late.

Leave a comment

Climate Change course – week 4

The IPCC recently published their Fifth Assessment Report (2013)report. Does the recent change in global temperatures reflect the predictions of climate models? Does the recent change in global temperatures reflect the predictions of climate models?

Whilst the press release says that models have predicted the recent change in global temps, the report itself (Chapter 9, box 9.2) mentions that the observed global mean surface temp over the last 15 yrs is below almost all model-simulated trends, whereas during the previous 15 yr period it was above. It discusses the relevance of short time period trends (10-15 yrs) to long term climate change, and the difficulties in predicting them. This issue highlights the danger of the abuse of statistics by selectively choosing which time period to study, which start time to base trends on, what factors to take into account etc. Climate modelling is clearly incredibly complex but vital, & improving all the time. In my humble opinion the case is made – we are causing damage, & for climate change deniers to mis-use or rubbish the hard work being done by climate scientists is disgraceful. We take out insurance to protect against things that we think may possibly happen with very low certainty, we visit the doctor if we think we may possibly have an illness; we are much more sure of the fact that humans are causing climate change so we should stop arguing about this & start acting-fast!

What is your view on geoengineering? Should it be used to prevent our planet warming? Post your views into the discussion.

My gut feeling is that we shouldn’t mess with nature – both in causing climate change or trying to geo-engineer our way out of it. I agree that the latter is a bit like a “get-out-of-jail free card”, to say nothing about the damage some of the schemes could cause. Far better to concentrate our efforts on preventing further damage (reducing/halting emissions, energy efficiency, reducing population growth, sustainable energy production etc). That said, I have no objection to people painting their roofs white, or any other “harmless” ideas like this – I suppose the question is “what is harmless & how do we find out?” . A classic case of How do I get to A from here? Don’t start from here! Apologies for the simplistic answer – better leave it to more learned people to decide…


Leave a comment

Climate Change course – week 3

Is a warming world likely to have more rain, or does it depend on where on Earth you are?

Exploring the map shows that while in the UK 2012 was the wettest on record, other parts of the world (US, Brazil, W.Australia, S.China) had severe droughts. Presumably the increase in hurricane activity in the Atlantic has a big effect on UK rainfall, & in turn is influenced by temperatures in N & S America. From what we have already learnt, a warming world will have more rain (until the oceans evaporate & we dry up!) but whether this map provides further evidence of climate change or adds complexity to the issue I don’t know – I am confused – as ever…

 What places on Earth have experienced the largest warming from 1980-2004? Are the areas that are experiencing the most warming also showing the largest variability in temperature and or precipitation?

Northern hemisphere predicted to have largest warming by 2050-74 compared to 1980-04 (if I have understood the question correctly) though if you look at 2070-95 that is spreading south to most land masses. Variability in temp (again if I have understood question right) appears similar (0.8-1.0) in most countries. But with precipitation, variability is much less in the northern regions compared to the south. Equator predicted to get increased precipitation over the period in question with less pronounced changes in north & south. More explanation on variability (ie standard deviations) needed – is it variability between each year in the period (eg 2050-74) being modelled, or between the various models being used?

What would you consider the largest threats from extreme weather events to where you live?

Other examples: increased atmospheric water vapour, decreases in the extent of mountain glaciers, snow cover, permafrost and Arctic sea ice. Largest threats here in UK are increased flooding from sea level rises, storms caused by changes to the jet stream & Atlantic conditions affected by melting Arctic sea-ice & hotter temps in US. Also increased pollution from fossil fuel emissions unless we get our act together! All the threats mentioned to public health, coastal infrastructure, agricultural productivity as well as damage to private & commercial property (eg Somerset levels right now).

The World Bank publishes a variety of environmental data, including carbon emissions (measured in kt). Create a graph to show a variety of countries at different levels of economic development by following this link to the World Bank web site. Include the USA and China in your graph. Share your graph in the discussion. You may also want to try plot carbon dioxide emissions measured in metric tons per capita. What conclusions can you draw?
In overall emissions, US long time big offender but China powering away from them. Other countries shown are relatively lower levels. But per capita, US & Australia highest although latter levelling off/falling slightly. But, other countries shown (including UK – shame!) show increasing per capita rates with exception of India. Worrying in countries where population is increasing as well – especially China where change in One child policy likely to cause pop. increase on top of rising per capita emissions. Conclusion – we need to control pop growth & per capita emissions at the same time.

Reflections on Week 3:

This week highlighted for me the problems of interpreting the mass of data that exists & drawing meaningful conclusions. I found session 3.4 “Your warming world” quite difficult & the questions maybe badly worded (sorry!). I could do with more explanations on the topic & perhaps the correct answers? I didn’t do any further research because I felt overwhelmed with statistics & didn’t think I could take any more…

Leave a comment

Climate Change course – week 2

A summary of learning this week so far:

Early Earth warmer than today in spite of sun being fainter. Thicker blanket of gases, especially water vapour & CO2 kept planet warm. Levels of CO2 gradually reduced through weathering by which it dissolved in rainwater to form weak carbonic acid which washed into the hydrosphere, got used by sea creatures to form shells & in turn got deposited on ocean floor becoming sedimentary rock. As sun warms up thus increasing temperature on Earth this negative feedback accelerates, cooling the planet by removing CO2 from the atmosphere & reducing its effect as a greenhouse gas.

Ice sheets at the poles grow over time due to decreasing temperatures & this increases their albedo effect. If the ice sheets reach a tipping point where they cover a large part of the Earth’s surface reaching down to the tropics – or where Texas is today – there is not enough of the Earth’s surface free of light-reflecting ice to warm the planet up & so it completely freezes over.

CO2 pumped into the atmosphere by volcanic activity cannot get back into the lithosphere via weathering due to the total ice cover of snowball Earth. A blanket of CO2 builds up in the atmosphere & gradually causes the Earth’s temperature to warm up. This starts to melt the ice sheets, decrease the albedo effect & allow weathering to happen all over again.

What are climate change records?

Data collected in the past from a variety of sources – ships, weather stations & more recently satellites, together with examination of tree ring growth, ice cores, rock sediment layers etc.  Data has to be adjusted to take account of different measuring techniques, errors, bias etc & allowance has to be made for local conditions where the measurements were made such as urban development, rainfall patterns, tree growth etc.

How do volcanoes affect climate change?

Volcanoes pump huge amounts of particles (aerosols) into the atmosphere.  These include ash, sulphur dioxide & other gases, yielding sulphates.  These aerosols seed clouds which together with the aerosols themselves reflect about a quarter of the sun’s energy back into space.  Some aerosols also absorb sunlight & different aerosols reflect or absorb sunlight in varying ways depending mainly on their colour & composition.  Lighter particles tend to reflect light & darker ones to absorb it.  As the particles erupted from volcanoes can remain in the upper atmosphere for several years before settling back to Earth they can have a major influence on temperature, not only because of their reflecting or absorbing properties but also because they have an albedo effect.  When the particles do fall back to Earth, where they land on ice & snow they can decrease the albedo effect by darkening the surface.   Finally the clouds seeded by particles contain a large number of smaller water droplets compared to clouds formed by clean air & these clouds are denser, whiter & very reflective of sunlight which has a cooling effect on the planet.  The effect of particles in the atmosphere is extremely complex because of all the different factors involved & the difficulty of measuring these particles.  Techniques are improving all the time.

How is today’s warming different from the past?

Using all the data collected from the past (described above) scientists can see that although global temperature has always varied by several degrees in either direction, today the rate of change is much faster.  Whereas in the past million years as Earth came out of ice ages temperatures rose by 4 to 7 degC over a period of about 5000 years, in the past century temperature has risen by 0.7 degC – about ten times faster than the rate of ice age recovery warming.  The predicted rate of warming for the next century is about 20 times faster.

What is the role of isotopes in determining temperatures from the past?

Examination of the calcium carbonate in the shells of small animals which have been deposited in sediment to determine the ratio of the two naturally-occurring stable isotopes of oxygen (16O & 18O)  gives an indication of the temperature at the time the carbonate was dissolved in the oceans.   This is because the isotropic ratio in the oxygen varies slightly depending on the temperature of the surrounding water, but this is complicated by the fact that the isotropic ratio in the oxygen in the shells depends on the same ratio in the surrounding sea water which also varies.  This variation is due to the fact that as water evaporates, the lighter molecules of water – those with atoms of oxygen (16O) – tend to evaporate before those with the 18O atoms.  When water then condenses, the heavier molecules (ie. with 18O oxygen atoms) condense first.  This makes the data very hard to interpret.

How have trees been used to reconstruct different climate variables across the world?

By examining tree rings scientists can work out the climatic conditions at the time – thicker rings indicate more growth due to factors such as rainfall, temperature etc.

How can ice cores provide a record of atmospheric composition?

Layers in ice created by change in texture of the ice surface during summer (24 hours of sunlight) making it different from layers of snow beneath it.  Examining thickness of ice over the years shows climatic conditions such as amount of snow, temperature, composition of the atmosphere & wind patterns (by taking readings from different ice cores in an area).    The ratio of oxygen isotopes (as above in sediment) shows temperature (this time of the air) at the time.  Can also measure the temperature of the ice directly in the middle sections (away from influence of surface temp & temp of the earth’s core) where it will barely have changed since it was formed.  By examining the bubbles of gas in the ice you can see the composition of gases in the atmosphere at the time.  Lastly any particles blown onto the ice settle in the layer & can be analysed to determine wind patterns & volcanic activity.  However, ice core analysis only shows what conditions were like on the parts of the Earth’s surface where they were taken from, not globally, although they do hint at global conditions.

What are the most important themes you have learned this week?   Self-regulating nature of Earth’s climate in the past, feedback mechanisms (+ & -), long & short term forcing factors.

What aspect of this week did you find difficult?  The discussion on isotopes & trying to relate the climate in the Pliocene to today’s in order to examine what might happen in the future – getting very involved!

What did you find most interesting? And why? Snowball Earth topic – all new to me, & beautifully explained in the video.

Was there something that you learned this week that prompted you to do your own research?  Tried to read up about the Pliocene climate etc but got really bogged down in techy articles & gave up.

Are there any web sites or other online resource that you found particularly useful in furthering your knowledge and understanding?  Nothing in particular because so many were rather too technical.  The Met Office & NASA sites are interesting & tend to be easier to follow.  If there was more time to spend on this…

Leave a comment

Climate Change course – week 1

My reflections & attempt at answering the questions from week one of this interesting course:

Key questions:

  • What are the key scientific principles that explain climate change including the greenhouse (blanket) effect?  Radiation from the sun is partially absorbed by the Earth (on average 70%) with 30% being reflected back into the atmosphere as short wave heat radiation; some of this heat radiation is absorbed by “greenhouse” gases which then emit heat radiation, some of which comes back to the earth’s surface raising the Earth’s temperature by about 33 deg C.
  • What are the key feedback mechanisms that help to explain why our climate is able to “self-regulate”?  Water vapour, ice albedo, radiation
  • How can our climate be conceptualised as a system containing a series of components that interact with one another?   5 components: the atmosphere, the hydrosphere (oceans, rivers etc), the biosphere (plants, vegetation), the cryosphere (snow & ice) & the lithospere (rocks etc); all interact to affect the flow of water vapour around the Earth’s surface which in turn affects the climate.

Also consider:

  • What are the most important themes you have learned this week?  The science behind the term greenhouse gases & why these gases affect climate – the fact that they are really acting more like a blanket than a greenhouse.  Also the albedo mechanism – I haven’t come across the term before.


  • What aspect of this week did you find difficult? Concentrating on the science – especially the Planck Stefan-Boltzmann law – don’t really understand it & looking it up is scary!
  • What did you find most interesting? And why? It was all interesting – hard to pick any one thing out.  Good to have it explained in small, easy(ish) to grasp steps & to be able to read/watch them over & over again.
  • Was there something that you learned this week that prompted you to do your own research?  I tried to look up the Planck Stefan-Boltzmann law but found it too difficult to understand – may have another go later on.
  • Are there any web sites or other online resource that you found particularly useful in furthering your knowledge and understanding?  Re the above, all the websites I tried looked too scientific for me – even Wikipedia!

Looking forward to Week 2!