Category Archives: long term targets

Simple approximations can link emissions and temperature rise

Some simple indicators based on stylised emissions tracks help show clearly the consequences of different rates of emissions reductions.

A simple relationship allows the overall objectives – limiting temperature rises and reducing emissions – to be linked in a straightforward way[i]. Over relevant ranges and timescales temperature rise varies approximately linearly with cumulative emissions of CO2, after adjusting for the effect of other greenhouse gases.  Specifically, for every 3700 GtCO2 emitted (1000GtC) the temperature will rise by about 2.0 degrees[ii] (with estimates in the range 0.8 to 2.5 degrees)[iii].  This is the transient climate response to cumulative emissions (TCRE).

There has been around a 1.0 degree rise in temperatures to date[iv].  This means the remaining total of cumulative emissions (“carbon budget”) needs to be small enough to keep further temperature rises to around 0.5 to 1.0 degrees if it is to meet targets of limiting temperature rises to 1.5 to 2.0 degrees.

The remaining carbon budget for meeting a 1.5 degree target (with 50% probability) is around 770 GtCO2.  The remaining carbon budget for meeting a 2 degree target (again with 50% probability) is 1690 GtCO2[v].  This is illustrated in Chart 1, which shows temperature rise (median estimates) against additional emissions from 2018.

There are many uncertainties in the estimates of the remaining carbon budget.  These include different estimates of the climate sensitivity, variations in warming due non-CO2 pollutants, and the effect of additional earth system feedbacks, including melting of permafrost.  These can each change the remaining carbon budget by around 200GtCO2 or more.

Chart 1: Temperature rise from additional emissions

 

Source: adapted from Table 2.2 in http://report.ipcc.ch/sr15/pdf/sr15_chapter2.pdf

To look at the implications of this simple relationship we can make the following assumptions about future levels of emissions.  These are simplistic, but like all useful simplifications, allow the essence of the issue to be seen more clearly.

  1. Net emissions continue approximately flat at present levels (of around 42 GtCO2a.[vi]) until they start to decrease.
  2. Once net emissions start decreasing they continue decreasing linearly to reach zero – when any continuing emissions are balanced by removals of COfrom the atmosphere. They then continue at zero. There are of course many other emissions tracks leading to the same cumulative emissions.  For example, many scenarios include negative total emissions, that is net removal of carbon dioxide from the atmosphere, in the second half of the century.
  3. Relatively short-lived climate forcings, such as methane, are also greatly reduced, so that they eventually add about 0.15 degrees to warming[vii].

Chart 2 shows various temperature outcomes matched to stylised emissions tracks.  Cumulative emissions are the areas under the curvesTo limit temperatures rises to 1.5 degrees, emissions need to fall to zero by around 2050 starting in 2020, consistent with the estimates in the recent IPCC report[viii].

For limiting temperature rises to 2 degrees with 50% probability, zero emissions must be reached around 2095To reach the 2 degree target with 66% probability emissions need to be reduced to net zero about 20 years earlier – by around 2075 from a 2020 start.  |To reach a target of “well below” 2 degrees is specified in the Paris Agreement emissions must be reduced to zero sooner.

Chart 2: Stylised emissions reduction pathways for defined temperature outcomes (temperatures with 50% and 75% probability)

This simplified approach yields some useful rules of thumb.

Each decade the starting point for emissions reductions is delayed (for example from 2020 to 2030) adds 0.23 degrees to the temperature rise if the subsequent time taken to reach zero emissions is the same (same rate of decrease – i.e. same slope of the line) – see Chart 3 below. This increase is even greater if emissions increase over the decade of delay.  This is a huge effect for a relatively small difference in timing.

Delaying the time taken to get to zero emissions by a decade from the same starting date (for example reaching zero in 2070 instead of 2060) increases eventual warming by 0.11 degrees.

Correspondingly, delaying the start of emissions reductions increases the required rate of emissions reduction to meet a given temperature target.  For each decade of delay in starting emissions reductions the time available to reduce emissions to zero decreases by two decades.  For example, tarting in 2020 gives about 75 years to reduce emissions to zero for a 2 degrees target.  Starting in 2030 gives only 55 years to reduce emissions from current levels to zero once reductions have begun, a much harder task.

Chart 3: Effect of delaying emissions reductions (temperatures with 50% probability)

These results are, within the limits of the simplifications I’ve adopted, consistent with other analysis (see notes at the end for further details)[ix].

How realistic are these goals? Energy infrastructure often has a lifetime of decades, so the system is slow to change.  Consistent with this, among major European economies the best that is being achieved on a sustained basis is emissions reductions of 10-20% per decade.  While some emissions reductions may now be easier than they were, for example because the costs of renewables have fallen, deeper emissions cuts are likely to be more challenging.  This implies many decades will be required to get down to zero emissions.

All of this emphasises the need to start soon, and keep going. The recent IPCC report emphasised the challenges of meeting a 1.5 degree target.  But even the target of keeping temperature rises below 2 degrees remains immensely difficult.  There is no time to lose.

Adam Whitmore – 23rd October 2018

Notes

[i] This analysis draws on previous work by Stocker and Allen, which I covered a while back here: https://onclimatechangepolicydotorg.wordpress.com/2013/12/06/early-reductions-in-carbon-dioxide-emissions-remain-imperative/

[ii] This is the figure implied in Table 2.2 in http://report.ipcc.ch/sr15/pdf/sr15_chapter2.pdf.  All references to temperature in this post are to global mean surface temperatures (GMST).

[iii] IPCC Fifth Assessment Report, Synthesis Report, Section 2.2.4 for the range.  The central value is that which appears to have been used to construct Table 2.2 of http://report.ipcc.ch/sr15/pdf/sr15_chapter2.pdf

[iv] The IPCC quotes 0.9 degrees by 2006-2015, which is consistent with 1.0 degrees now.

[v] Table 2.2 of http://report.ipcc.ch/sr15/pdf/sr15_chapter2.pdf

[vi]  http://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdfC1.3

[vii] See IPCC 1.5 degree report Chapter 2 for details.

[viii] http://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdf summary for policy makers, see charts on p.6

[ix] See for example work by Climate Action Tracker https://climateactiontracker.org/global/temperatures/, and and the Stocker and Allan analysis cited as reference (i) above.  The recent IPCC report Chapter 2 Section C1, concludes:  In model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030 (40–60% interquartile range), reaching net zero around 2050 (2045–2055 interquartile range). For limiting global warming to below 2°C CO2 emissions are projected to decline by about 20% by 2030 in most pathways (10–30% interquartile range) and reach net zero around 2075 (2065–2080 interquartile range). Non-CO2 emissions in pathways that limit global warming to 1.5°C show deep reductions that are similar to those in pathways limiting warming to 2°C.”  References in this paragraph to pathways limiting global warming to 2C are based on a 66% probability of staying below 2C.

 

 

Five years on

The past five years have given many reasons for optimism about climate change

I have now been writing this blog for just over five years, and it seems timely to step back and look at how the climate change problem appears now compared with five years ago.

In some ways it is easy to feel discouraged.  In the last five years the world has managed to get through about a tenth of its remaining carbon budget, a budget that needs to last effectively forever.

However, in many ways there seem to be reasons for much greater optimism now than five years ago.  Several trends are converging that together make it appear that the worst of the risks of climate change can be avoided.

There is increasing action at the national level to reduce emissions, reinforced by the Paris Agreement …

Legislation is now in place in 164 countries, including the world’s 50 largest emitters.  There are over 1200 climate change and related laws now in place compared with 60 twenty years ago[i].  And this is not restricted to developed countries – many lower income countries are taking action.  Action at national level is being supported around the world by action in numerous cities, regions and companies.

This trend has now been reinforced by the Paris Agreement, which entered into force in November 2016, and commits the world to limiting temperature rises and reducing emissions.

There is increasing evidence of success in reducing emissions …

Many developed countries, especially in Europe, have shown since 1990 that it is possible to reduce emissions while continuing to grow their economies.  Globally, emissions of carbon dioxide from energy and industry have at least been growing more slowly over the past four years and may even have reached a plateau[ii].

Carbon pricing is spreading around the world  …

Among the many policies put in place, the growth of carbon pricing has been especially remarkable.  It has grown from a few small northern European economies 15 years ago to over 40 jurisdictions[iii].  Prices are often too low to be fully effective.  However, carbon pricing has also been shown to work spectacularly well in the right circumstances, as it has in the UK power sector.  And the presence of emissions caps in many jurisdictions gives a strong strategic signal to investors.

Investors are moving out of high carbon sources and in to lower carbon opportunities …

Companies are under increasing pressure to say how their businesses will be affected by climate change and to do something about reducing emissions.  And initiatives such as the Climate Action 100+, which includes over two hundred global investors controlling over $20 trillion of assets, are putting pressure on companies to step up their action.  This will further the trend towards increasing investment in a low carbon economy.  Meanwhile, many funds are divesting from fossil fuels, and vast amounts of capital are already going into low carbon investments.

Falling costs and increasing deployment of renewables and other low carbon technologies …

Solar and wind power and now at scale and continuing to grow very rapidly.  They are increasingly cost-competitive with fossil fuels.  The decarbonisation of the power sector thus looks likely to proceed rapidly, which will in turn enable electrification to decarbonise other sectors.  Electric vehicle sales are now growing rapidly, and expected to account for the majority of light vehicle sales within a couple of decades.  Other technologies, such as LED lighting are also progressing quickly.

This is not only making emissions reductions look achievable, it is making it clear that low carbon technologies can become cheaper than the high carbon technologies they replace, and can build whole new industries as they do.  As a reminder of just how fast things have moved, in the last five years alone, the charts here show global generation from wind and solar since 2000.

Falling costs of low carbon technologies, more than anything else, gives cause for optimism about reducing emissions.  As lower carbon alternatives become cheaper the case for high carbon technologies will simply disappear.

Charts: Global Generation from Wind and Solar 2000 – 2017

Sources:  BP Statistical Review of World Energy, Enerdata, GWEC, IEA

Climate sensitivity looks less likely to be at the high end of the range of estimates …

The climate has already warmed by about a degree Celsius, and some impacts from climate change have been greater than expected.  However, the increase in temperature in response to increasing concentrations of greenhouse gases has so far shown few signs of being towards the top end of the possible range, although we can never rule out the risk of bad surprises.

Taking these trends together there is reason to be cautiously optimistic …

There will still be serious damage from climate change – indeed some is already happening.  And it is by no means clear that the world will act as quickly as it could or should.  And there could still be some nasty surprises in the earth’s reaction to continuing emissions.  Consequently, much effort and not a little luck is still needed to avoid the worst effects of climate change.

But compared with how things were looking five years ago there seem many reasons to believe that things are beginning to move in the right direction.  The job now is to keep things moving that way, and to speed up progress.

Adam Whitmore – 10th April March 2018 

[i] http://www.lse.ac.uk/GranthamInstitute/publication/global-trends-in-climate-change-legislation-and-litigation-2017-update/

[ii] http://www.pbl.nl/sites/default/files/cms/publicaties/pbl-2017-trends-in-global-co2-and-total-greenhouse-gas-emissons-2017-report_2674.pdf

[iii] https://openknowledge.worldbank.org/handle/10986/28510

Economic growth and emissions cuts can go together

There is often said to be a trade-off between growth and decarbonisation, but the evidence shows that advanced economies can combine large emissions cuts with continuing economic growth.

Policy on greenhouse gas emissions reductions is often framed as a trade-off between greater emissions reductions and greater economic growth.  However, while emissions clearly can’t be reduced to zero immediately, faster emissions reductions can be accompanied by robust economic performance.  The clearest example of this is the UK.  Since 1990 the UK has cut its total greenhouse gas emissions much more rapidly than other G7 countries, while growing its economic output per capita more than the average.  This is illustrated in Chart 1.

Chart 1: UK per capita GDP growth and greenhouse gas emissions compared with the G7 average[i]

The extent by which the UK has cut its per capita emissions relative to other countries is emphasised in the following charts, which show that the UK has achieved by far the largest reductions in per capita CO2 emissions.

Chart 2: CO2 emissions per capita in 2016 and 1990 for G7 countries[ii]

Note: Japanese emissions rose by 0.4 tonnes per capita over the period (not shown)

Chart 3: Change in per capita and total CO2 emissions 1990 to 2016 for G7 countries

Note: Data in these charts is for CO2 only, excluding other greenhouse gases.

Of course, some of the relative changes reflect circumstances.  The UK started with relatively high emissions, including extensive use of coal in power generation.  In contrast, France already had a low carbon power sector in 1990, and in 2016 France’s per capita emissions remained about 8% below those of the UK, even though UK emissions had fallen much more from their 1990 levels.

Germany has also achieved significant reductions, having benefitted from reductions in emissions in the former East Germany and installing large amounts of renewables.  However it has been hampered by continuing extensive use of coal and lignite for power generation.  The USA has accommodated significant population growth with only a small rise in emissions, but this is clearly nowhere near enough if it is to make an appropriate contribution to global reductions.  Emissions remain at almost three times UK levels.  Canadian emissions are also high and have increased in absolute terms.  Japan’s emissions have grown slightly over the period.

Some falls in emissions in G7 economies may reflect a shift in the global pattern of emissions, with reduced emissions from industry in the G7 economies balanced by increases in China and elsewhere.  However this can’t account for all of the reductions that have been achieved, or the vast differences in reductions between countries.

Policy has certainly also played its part.  UK policy has successfully targeted relatively low cost emissions reduction, notably reducing coal use in the power sector.  Above all the Climate Change Act (2008) has provided a consistent and rigorous policy framework.

And whatever the reason, one thing is clear.  Cutting emissions more can accompany growing the economy more.

Adam Whitmore – 8th March 2018

 

 

[i]https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/651916/BEIS_The_Clean_Growth_online_12.10.17.pdf

[ii] http://www.pbl.nl/en/publications/trends-in-global-co2-and-total-greenhouse-gas-emissions-2017-report

The case for additional actions in sectors covered by the EUETS is now even stronger

Recently agreed reforms to the EUETS mean that excess allowances in the MSR will be cancelled.  This further strengthens the case for actions such as phase-out of coal plant, increasing energy efficiency and deploying more renewables.

About a year ago I looked at whether additional actions to reduce emissions in sectors covered by the EUETS do in practice lead to net emissions reductions over time [i].

It is sometimes claimed that total emissions are always equal to the fixed cap.  By implication additional actions do not reduce total emissions, because if emissions are reduced in one place there will be a corresponding increase elsewhere.  This is sometimes called the “waterbed hypothesis” by analogy – if you squeeze in one place there is an equal size bulge elsewhere.

Although often repeated, this claim is untrue.  Under the EU ETS at present the vast majority of emissions reductions from additional actions will be permanently retained, reflecting the continuing surplus of allowances and the operation of the MSR.  Furthermore, over the long term the cap is not fixed, but can respond to circumstances.  For example, tighter caps can be set by policy makers once emissions reductions have been demonstrated as feasible.

When I last looked at this issue, the fate of additional allowances in the MSR remained necessarily speculative.  It was clear that additional excess allowances would at least not return to the market for decades.  It also seemed likely that they would be cancelled.  However, no cancellation mechanism was then defined.

This has now changed with the trilogue conclusions reached last week, which include a limit on the size of the MSR from 2023.  The limit is equal to the previous year’s auction volume, and is likely, given the size of the current surplus, to lead to large numbers of allowances being cancelled in the 2020s.

With this limit in place there is a very clear pathway by which allowances freed up by additional actions, such as reduced coal burn or increased renewables, will add to the surplus, be transferred to the MSR then cancelled (see diagram).  Total emissions under the EUETS will be correspondingly lower.

There is now a clear mechanism by which additional actions reduce total emissions

Modelling confirms that with the limit on the size of the MSR in place a large majority of reductions from non-ETS actions are retained, because additional allowances freed up almost all go into the MSR, and are then cancelled.  This is shown in the chart below for an illustrative case of additional actions which reduce emissions by 100 million tonnes in 2020.  Not all of the allowances freed up by additional actions are cancelled.  First there is a small rebound in emissions due to price changes (see references for more on this effect).  Then, even over a decade, the MSR does not remove them all from circulation.  This is because it takes a percentage of the remainder each year, so the remainder successively decreases, but does not reach zero.  If the period were extended beyond 2030 a larger proportion would be cancelled, assuming a continuing surplus.  Nevertheless over 80% of allowances freed up by additional actions are cancelled by 2030.

The benefit of additional actions is thus strongly confirmed.

The large majority of allowances freed up by additional actions are eventually cancelled

Source: Sandbag

When the market eventually returns to scarcity the effect of additional actions becomes more complex.  However additional actions are still likely to reduce future emissions, for example by enabling lower caps in future.

Policy makers should pursue ambitious programmes of additional action in sectors covered by the EUETS, confident of their effectiveness in the light of these conclusions.  Some of the largest and lowest cost gains are likely to be from the phase out of coal and lignite for electricity generation, which still accounts for almost 40% of emissions under the EUETS.  Continuing efforts to deploy renewables and increase energy efficiency are also likely to be highly beneficial.

Adam Whitmore – 15th November 2017

[i] See https://onclimatechangepolicydotorg.wordpress.com/2016/10/21/additional-actions-in-euets-sectors-can-reduce-cumulative-emissions/  For further detail see https://sandbag.org.uk/project/puncturing-the-waterbed-myth/ .  A study by the Danish Council on Climate Change reached similar conclusions, extending the analysis to the particular case of renewables policy.  See Subsidies to renewable energy and the european emissions trading system: is there really a waterbed effect? By Frederik Silbye, Danish Council on Climate Change Peter Birch Sørensen, Department of Economics, University of Copenhagen and Danish Council on Climate Change, March 2017.

New long term targets for emissions reduction are needed.

The UK and other jurisdictions need to set target dates for reaching net zero greenhouse gas emissions.  These need to be reinforced by new targets for 2060 that are at least close to zero, and by reaffirmed or strengthened targets for 2050.

Ten years ago setting emissions reduction targets for 2050 was a major step forward

2018 sees the tenth anniversary of the UK’s Climate Change Act[i].  This remarkable piece of legislation established a legally binding obligation for the UK to reduce its greenhouse gas emissions by 80% from 1990 levels by 2050, with obligations along the way in the form of five year carbon budgets.  So far progress has been remarkably good, though significant challenges remain.

Other jurisdictions also adopted 2050 targets at around the same time.  In 2005 California also set a target of an 80% reduction from 1990 levels[ii].  In October 2009 the EU established a long term EU goal for reducing emissions by 80-95% from 1990 levels by 2050[iii].

At the time these targets were path breaking.  However, ten years on there are good reasons for reviewing and extending them.

But now the world has moved on …

  • When the targets were established, the period to 2050 seemed long enough to give appropriate strategic guidance to policy makers and investors. However, future dates are now ten years closer.  A 2060 target now gives about the same time horizon for planning as the 2050 targets did when they were established.
  • The Paris Agreement sets targets to limit temperature rises which imply stringent limits on cumulative emissions. It also sets a goal of net zero global emissions in the second half of the century.
  • A fifth or more of the world’s carbon budget that remained in 2008 has since been used up[iv], increasing the urgency of emissions reductions.

Extending targets to reflect these changes would have some clear benefits … 

Together these changes imply a strong case for setting new targets now.

The most compelling target would be a date by which emissions must fall to net zero.  Such a target would make it clear to all sectors that they need to completely decarbonise by a specified date.  At the moment emissions of up to 20% of 1990 levels are allowed even in 2050.  This allows each of those sectors where decarbonisation is more difficult – for example parts of industry, agriculture or residential heating – to largely continue in a belief that there will still be plenty of room for them within the 2050 emissions limit, even though this cannot be true for most sectors.  This in turn allows them to continue to believe they can carry on indefinitely without taking the steps needed to decarbonise.  A date for reaching zero makes it clear this can’t happen.

Setting stringent target for 2060 – at or close to zero – would also give investors in low carbon infrastructure greater confidence, and deter investment in higher carbon alternatives. In the case of the UK and California, a simple extrapolation of their current targets would suggest a 2060 target of a 93% reduction from 1990 by 2050, reaching zero by 2065.

As part of the process of setting these longer term goals the existing 2050 targets need to be at least reaffirmed and preferably tightened.  If this is not done there is the risk that policy makers will simply see the problem as having become more distant, and delay action.  This is the last thing that the climate needs.

2050 targets may also need to be revised …

As a first step, the EU’s target of 80-95% cuts clearly needs to be made more precise.  The current uncertainty of a factor of four in the level of emissions allowed in 2050 is too wide for sensible policy planning.

However the events of the last ten years also raise the question of whether the stringency of the 2050 targets need to be increased, with implications for later periods.  The UK Government’s former Chief Scientific Adviser Sir David King and others have suggested that there is a strong case for the UK seeking to reach net zero emissions by 2050[v].  The difference in cumulative emissions in declining linearly to net zero by 2050 instead of by 2065 is substantial, at a little over 3 billion tonnes – equivalent to about 8 years of current UK emissions.

The goal of reaching zero emissions by 2050 is clearly desirable in many ways.  However there is a risk that it may have unwanted side effects.  The government’s advisory body, the Committee on Climate Change has pointed out that policies are not in yet place even to meet current goals for the fifth carbon budget in around 2030[1].  The route to net zero emissions in 2050 – just over 30 years from now – looks even less clear.  Indeed reaching that goal even by 2065 remains challenging.  If even tighter targets are introduced they may come to be regarded as unrealistic, which may in turn risk weakening commitment to them.  A somewhat slower emissions reduction track may prove a relatively acceptable price to pay for retaining the credibility and integrity of the targets.

Whatever the judgement on this, the need for longer term targets is clear.  Governments need to set dates for reaching net zero emissions.  These need to be supported by targets for 2060 that specify continued rapid reductions in emissions after 2050, and by reaffirmation of 2050 targets, tightening them as necessary.  These new targets will in turn help stimulate the additional actions to rapidly reduce emissions that are ever more urgently needed.

Adam Whitmore – 6th November 2017

 Notes:

[1] https://www.theccc.org.uk/publication/2017-report-to-parliament-meeting-carbon-budgets-closing-the-policy-gap/

[i] https://www.theccc.org.uk/tackling-climate-change/the-legal-landscape/the-climate-change-act/

[ii] https://www.arb.ca.gov/cc/cc.htm

[iii] https://www.consilium.europa.eu/uedocs/complementary measures_data/docs/pressdata/en/ec/110889.pdf

[iv] The calculation is based on data in the IPCC Fifth Assessment Report, Synthesis Report.  This quotes a  cumulative budget of 3700 billion tonnes of CO2 for a two thirds probability of staying below 2 degrees.  Of this 1800 billion tonnes had been used by 2011.  Assuming CO2 emissions of roughly 40 billion tonnes p.a. including land use gives a remaining budget in 2008 of 1920 billion tonnes.  Over the subsequent ten years about 400 million tonnes CO2, which is just over a fifth of 1920 billion tonnes, have been emitted.

[v] http://www.independent.co.uk/environment/ministers-greenhouse-gas-emissions-fail-cut-environment-greg-clark-chief-scientist-david-king-a7969496.html