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Chapter Three - What is Meant by Controlling Climate Change?

I'm writing this a fortnight earlier than planned in order to give readers the chance of a summer-break free from the thoughts of Climate Change.  We all need a rest!

Dangerous Climate Change

Based on best available scientific evidence, it is clear than increases in CO2, and other greenhouse gas CO2e (carbon dioxide equivalent), which consitute F in the Kaya Identity (see earlier), result in temperature elevation.  The relationship between the two is known as climate sensitivity.  It is accepted by most scientists that a CO2 doubling (from pre-industrial 280ppm to 550ppm) will probably lead to a roughly 3C temperature rise.  Dependent on the emission scenario, the IPCC calculated a range of between 1.5C and 4.5C.  Unfortunately, this is far from exact since fossil records estimate that climate sensitivity could be as high as 6C (Hansen).

Are temperature increases dangerous?  The overriding consensus is a resounding yes.  There is no question that biomes, including pathogenic species, would survive and even proliferate.  The concern is that widespread ecosystem collapse would occur specifically with regard to biomes on which humans depend.  For the human civilization existence of the last 6,000 years there has been near constancy in global climate.  The next 100 years will almost certainly be very different.  The question is from the point of view of our civilization: fatally different, or just seriously different?

Lynas, in his book Six Degrees (2007), collated hundreds of scientific reports to explore the probable effects of different temperature increases over the coming century.  Whilst to some degree conjecture, they are nonetheless a good departure point for discussion.

Impacts at 2C

Lynas predicted: thirsty cities; acidic oceans; annual summer heat waves like 2003; and a hot Mediterranean climate like the Sahara.  He also listed: dying corals; irreversible Greenland melt; polar bear extinction threat; conflict over Arctic sea routes; Indian heat waves; waterless Peru; and Californian desiccation.  Food shortages would be the norm and biodiversity would be lost with the possibility of the onset of the 6th Mass Extinction.  For this temperature scenario, other sources have listed: disrupted ecosystems; concerns over water and food security; threats to health; rising sea levels; and cities at risk.  And, of course, we now have the damning IPCC report of 2018.

Impacts at 4C

Here, the effects become even more alarming with ocean encroachment an impossible challenge as witnessed at Holbeck Hall, Scarborough, UK in 1993.  Hundreds of millions of refugees would be stateless and worldwide agricultural drought would result.  Mediterranean regions would experience extreme heat, 45C temperatures would be recorded in the UK while mainland Europe would be as hot as the Middle East is today.  Lynas predicted that a State of Emergency would ensue as a result of these conditions.  Glaciers would vanish globally.  For the UK, house price rises could be expected as the country becomes a safe-haven Britain but these would be tempered by increasing Atlantic storms and flooding - while snowfall would become a freak event.

Globally, the potential dangerous development for 4C is that the Arctic Ocean ice disappears and the tundra melts to release subterranean carbon dioxide and methane.  An additional factor to consider here is vegetation decomposition since 1% of this potential carbon reservoir equates to a doubling of current emissions.

Impacts at 6C

Essentially, a near end of the world scenario would result.  This is not to say that some humans would be eking out an existence somewhere in the world but conditions would become so difficult as to be almost unbearable.


The concept of dangerous climate change is not new.  As early as the IPCC's Second Assessment in 1995 the concept was raised, and in 2002 the United Nations Framework Convention on Climate Change (UNFCCC) incorporated the statement in its Article 2 that the world needed to stabilize atmospheric greenhouse gas concentrations to prevent dangerous anthropogenic climate interference.

In 2005, a conference was held in the UK to discuss 'dangerous' climate change avoidance.  Based on the precautionary principle, it was agreed that a 2C limit should be the goal since higher temperature increases effect potentially large-scale adverse impacts as discussed above.  In terms of atmospheric gas concentration, 450ppm is consistent with a 50:50 chance of not exceeding 2C.  We are now at 415ppm (2019) with no sign of this abating anytime soon.

Given that 2019 concentrations exceeded 415ppm, a target of 450ppm may now be considered as ambitious although the 2C limit was adopted formally by both the EU in 1996 and in the 2009 Copenhagen Accord.  In Paris in 2015, a new aim of 1.5C was set but as we will see this lower target will require even more stringent action.

Recent Evidence

Evidence provided to the December 2015 Paris Climate Change Summit suggested that more stringent standards should be enforced.  Hansen, in the late 1980s, also strongly argued that the climate sensitivity is 6C not 3C for a doubling of CO2 (from pre-industrial concentrations) and advocated that temperature increase should be restricted to no more than 1C.  His CO2 atmospheric limit was 350ppm - which would necessitate an immediate emissions peak and subsequent reduction by carbon sequestration.  As we mentioned earlier, the Paris Summit has since agreed to a target 2C but aimed for 1.5C.

It is important to distinguish between emissions (a flow) and concentrations (stock).  Emissions are annual but concentrations build up over time. Global warming is a stock problem.  It is insufficient just to reduce or stop annual emissions - crucially we need to focus on the concentration in the atmosphere.  Since it takes time to reach equilibrium, targets may be overshot with disastrous consequences - positive feedbacks such as the release of methane are also a risk to climate.

The Danger

In summary, a target of 1.5C should be the goal with an upper limit of 2C.  The convincing arguments of Hansen over the years, and especially since his 1988 Senate testimony commend increased action to prevent irreversible climate change.  When natural disasters, refugee crises and system inertia are factored in it is not unreasonable to question whether adaption will be possible at all and, if so, how?  This is an issue, which is both global and intergenerational.

What to do about it

The fundamental problem is that carbon emissions are so inexorably linked to economic activity (IT, housing, agriculture, manufacture and transport) that reducing them and then operating a 'green' economy is a massive and very complicated mammoth task.  Thinking negatively, economy derailment could be the solution - although to be positive the focus should be major change along the continuum of slowing, stabilizing, and reducing CO2 emissions within a fully functioning economy, which runs counter to many environmentalists' thinking.  We need a new economy based on a clean-energy future.


A consensus for a 2C limit at 450ppm may be regarded as objective targets for limiting climate change.  The climate can never be controlled fully, and change is already underway due to system inertia.  Our aim must be to hold the average temperature to within a 50:50 chance of exceeding 2C provided this is under our effective control - but still strive for a 1.5C solution.

To meet this target, for 1.5C the world needs to achieve net zero carbon emissions by 2050, and a global reduction of 45% by 2030 from today's levels.  Since industrialized countries have the legacy of past emission (so-called 'carbon debt') they are obliged morally to reduce quicker still.  The UK, for example, has accepted a goal of 100% reduction by 2050 and an interim target of roughly 60% on 1990 levels by 2030.

Developing countries must also accept a share of quicker reductions however.  In Copenhagen in 2009 various countries committed to an Accord detailing their emission reductions.  This was strengthened at Paris in 2015.


If problem resolution cannot be found in our social and economic systems then weather interference through geo-engineering (deliberate large scale intervention in the Earth's natural systems to counteract climate change) could be considered.  Most options here, however, come with unpredictable consequences.  Scientists agree broadly that geo-engineering should not substitute for climate change mitigation efforts, which would be far cheaper.  Also, large uncertainties exist over the effectiveness of geo-engineering options.

Geo-engineering broadly consides two options: solar radiation management (SRM); and carbon dioxide removal (CDR). Types of SRM include: albedo enhancement; space reflectors; and stratospheric aerosols while CDR strategies include: afforestation; biochar; bio-energy with carbon capture and storage (BECCS); ambient air capture; ocean fertilization; enhanced weathering; and ocean alkalinity enhancement.

Tree-planting is currently in vogue - although this does not mean to say we can avoid mitigation efforts as a result.  Small trials of ocean fertilization have commenced but have proven controversial while other schemes such as ocean alkalinity enhancement interfere with the Earth's natural systems to such an extent that a temporary moratorium should be put on those programmes.

Economic Growth Tension

A clear tension exists between carbon emissions and economic growth since, for the past two centuries, the latter depended on cheap fossil fuels - with low cost energy fundamental to growth.  The challenge then is to 'decouple' effectively growth from carbon emisssions and so guarantee a clean energy future.  Integrated Assessment Models would argue here that we need optimal carbon taxes to effect this but these, in turn, would increase the costs of travel, food and goods at least in the short run.  Two fundamental problems that would need to be addressed here are the requirements for international co-operation between nations, and internal wealth transfers to the poor in society.  Of course, if we can - later on - access cheaper renewable energy then this, too, could be a driver of economic growth.

Anderson and Bows

According to analysis by Anderson and Bows (2008), stablization at 450ppm required, at least, global energy related emissions to peak by 2015, decline rapidly at a rate of 6 to 8% pa with full decarbonisation soon after 2050.  We have clearly overshot these targets.  They noted, however, that 450ppm is no longer a viable stabilization concentration and that the implications of this for climate change policy, particularly adaptation, are profound.

The climate, remember, is not negotiable.  We must strive for 450ppm at a minimum meaning we must also now examine how, maybe, to restrict (or, better, target) economic growth - at least for a while.  That link between economic growth and climate change will be considered further in Chapter 5 (due 1 October) after first discussiong economic growth per se next, after the summer holidays.


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Chapter One - The Kaya Identity & IPAT

Carbon dioxide is a greenhouse gas that is contributing to climate change by trapping solar infra-red rays within the atmosphere and, in turn, heating up the ocean and land temperatures.  Although other gases play a role, since 2000 the dominant gas is CO2.  CO2 is the biggest headache and therefore the focus in this blog.

The 'problem' of climate change is immensely complicated but, at the same time, the solution is very simple - we need to stop emissions.  Without getting too involved in the contradictions surrounding the subject (and often hypocritical actions), resolution can be simplified into one equation, the Kaya Identity, which was developed by a Japanese energy economist of the same name, Yoichi Kaya (1993):

           F = P * (G/P) * (E/G) * (F/E) = P * g * e * f


F is global CO2 emissions from human sources;

P is the global population;

G is world GDP (Gross Domestic Product) and g = (G/P) the global per-capita GDP;

E is global primary energy consumption and …

Chapter Two - What Is Climate Change?

I'm writing this as the latest climate-changed induced heatwave grips Europe (The World Meteorological Organisation has said the high temperatures are "absolutely consistent" with anthropogenic increases in greenhouse gases).  The mercury hit 45C in Montpellier, France, yesterday - a record high for June - as high as August in Death Valley.

Climate and Weather

Yet it is important to make a distinction between climate and weather.  According to, simple climate definitions include:

1. The composite or generally prevailing weather conditions of a region, as temperature, air pressure, humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years; and

2. A region or area characterized by a given climate: to move to a warm climate.

Weather is defined as:

1. The state of the atmosphere with respect to wind, temperature, cloudiness, moisture, pressure, etc.; and

2. A strong wind or storm or strong winds and storms colle…