Is it too late to limit global warming below 2°C or even 1.5°C?

It is not too late to keep global warming below 2 degrees Celsius, but current national pledges are inadequate. The longer we wait to take serious action the harder the task becomes. Time is rapidly running out.

Many claims have been made in media and policy circles that meeting the 2°C maximum warming goal is no longer possible, and that the goal called for by AOSIS and the LDCS to reduce warming below 1.5°C by 2100 cannot be met.

Others argue that closing the 2020 emissions gap is not important as there is still time for action after 2020, with ‘infinite’ emission pathways possible afterwards to limit warming to below 2°C. This briefing presents our analysis of these claims from a scientific and quantitative perspective.

We address key questions relating to the feasibility and practicality of limiting warming to these levels.

In summary, science clearly shows that:

--Limiting global warming to below 2°C maximum, or even reducing to below 1.5°C by 2100 remains technically and economically feasible, provided there is sufficient political ambition backed up by action to introduce the required measures and policy changes now.

--The window for reversing emission trends is rapidly narrowing. Emissions must be reduced by roughly 15% from present levels by 2020 to be on a pathway holding warming below 2°C and/or reducing warming to below 1.5°C by 2100.

--Entirely closing the emissions gap remains technically and economically feasible, but it can only be achieved by increasing ambition beyond the current pledges.

Do historical emissions prevent us from staying below 2°C?

No, they do not. It has been argued that the physics of the climate system will lead to warming exceeding 2°C because of past emissions, no matter what we do with emissions in the future. This is not true. If total global greenhouse gas emissions were, hypothetically, set to zero in 2016, “bestguess” temperature increase would not exceed 1.5°C. So from a purely geophysical point of view, 2°C remains within reach. Setting emissions to zero now is of course not realistic, but many technologically and economically feasible pathways that limit warming to these levels have been published.

Are there achievable emission pathways to stay below 2°C?

Yes, many. Many scenarios that simulate the global economy and associated energy system can simulate global pathways that are able to limit warming to below 2°C with a likely (>66%) chance, as well as return warming to below 1.5°C by 2100. Energy-economic scenarios show multiple options to limit warming to these levels, but delayed action brings increasing limitations and costs.

--These scenarios, available in the scientific literature, show that the order of magnitude of the cost of staying below 2°C can be less than 1% of global GDP4, when investments are spread over time. However, such scenarios show that coordinated early action (ie, starting now, well before 2020) will deliver the least cost way of staying below 2°C. The longer the delay, the higher the cost and the bigger the technological challenges.

--Scenario assessments show that when key mitigation technologies (like carbon-capture and storage) fail, temperature increase can still be kept below 2°C, provided substantial energy efficiency measures are implemented quickly to compensate. Science thus shows, with multiple technological paths available at moderate costs, that limiting warming to below 2°C is feasible from an economic and energy-system transition point of view.

How feasible is this really?

Very feasible, and very beneficial. The IEA Energy Technology Perspectives 2012 reported that:

“a technological transformation of the energy system is still possible, despite current trends. […] Investing in clean energy makes economic sense – every additional dollar invested can generate three dollars in future fuel savings by 2050. By 2025, the fuel savings realised would outweigh the investments.”

The new IEA World Energy Outlook’s ‘Efficient World Scenario’ shows that removal of policy and other barriers can tap the potential and provide huge co-benefits in energy security, economic growth and the environment, without requiring unexpected technological breakthroughs. The growth in global primary energy demand could be halved by 2035, producing a net gain in cumulative economic output of $18 trillion, or 0.4% of GDP through more efficient allocation of resources. Biggest GDP gains would be expected in India (3%), China (2.1%), the US (1.7%) and Europe (1.1%).

Why are 2020 emission levels important for the feasibility of the warming goals?

The longer we wait the more difficult it gets. The series of UNEP Gap reports provide a range of optimal pathways, with a focus on associated global emission levels by 2020 if one’s objective is to hold warming below 2°C with a ‘likely’ chance (>66%).

These scenarios find a global total emission range of 41-47 GtCO2e by 2020 (yellow path in Figure below). They require ambitious action before 2020, almost instantaneous change by all actors and reduction rates that are technically and economically feasible. They also provide opportunities for innovation and energy security.

Sixteen years ago, when the EU agreed on the 2°C limit, pathways compatible with 2°C were calculated that would have had lower global emissions in 2020 (green line in Figure below). These scenarios still would have required ambitious, but realistic reduction rates. They would have allowed delayed participation of developing countries and left significant options for different technologies.

Aggregates of current emission reduction pledges by all countries (the Copenhagen pledges) indicate that emissions in 2020 will be above the range of optimal reduction pathways (see red range in Figure below). 2°C scenarios with these higher 2020 levels (blue pathway in Figure below) would be more difficult to achieve (see next section).

What happens if governments fail to increase pledges and the 2020 emissions gap is not closed?

It will require much higher long-term and overall costs, a narrowing of options and choices for society, decreasing feasibility and increased climatic damages due to higher rates of climate change, ocean acidification and sea level rise.

Recent studies show that when no, or insufficient, coordinated action is taken before 2020, and emissions are left to increase through 2020, there are still options to limit warming to below 2°C through steeper and deeper emission cuts post-2020. However, these options are characterised by rapidly increasing risks and cost. Delays would lead to:

--Higher long-term and overall costs. These higher costs would have to be carried by the next generation(s): with estimates showing at least 50% higher costs around the 2050s;

--A higher dependence on the full potential of all mitigation technologies, including uncertain technologies, such as carbon capture and storage (CCS);

--More pressure on future policy requirements. For example, full global participation would be required after 2020, and society may have little freedom to choose technologies, such as the freedom to reject large-scale nuclear energy, CCS, or bio-energy.

--Increased climatic risks, like higher rates of warming and the probability of warming overshooting 2°C by a substantial margin. Continuation of the coal-intensive development reported in the IEA 2012 Word Energy Outlook leads to a significant chance of a warming of 4°C as early as the 2060s.

Are countries likely to meet their pledge?

Pledges have induced policy efforts in all countries and are likely to deliver emission reductions. Countries are developing and implementing national climate policies, but more action is needed to reach international pledges in most countries assessed.

There has been more action to reduce energy consumption and greenhouse gas emissions than ever since the start of international climate negotiations. Yet, for some governments these national policies are not sufficient to meet their international pledges.

We draw on other work we have been involved in, published this week in the report: “Greenhouse gas emission reduction proposals ad national climate policies of major economies”. This report assesses how likely the current national policies are to meet existing pledges. We set this in the context of the overall level of ambition of the individual pledges as assessed in our Climate Action Tracker.

Our findings, summarised below, indicate that while there are some countries likely to achieve, or even exceed, their pledge, the aggregated emissions level from all countries’ pledges is still likely to exceed a 2°C increase of temperature by a wide margin, unless pledges are improved and more policies implemented on a national level.


Summary assessment of major emitters’ pledges

China – pledge ambition is rated inadequate with large data uncertainty and likely to be met: Meeting the inadequate pledge, China will still continue rapidly increasing GHG emissions to about 14 GtCO2e in 2020 according to China’s second National Communication – and our own calculations.

USA – pledge ambition is rated inadequate and unlikely to be met: The pledge represents a 3% reduction below 1990. All effort-sharing approaches would require more stringent reductions. Even though the latest official projections from the US EIA indicate lower emissions, this can only partly be attributed to policies and will not be sufficient to meet the pledge.

EU – pledges ambition is rated inadequate and likely to be met: According to its own projections, EU is expecting to meet its unconditional pledge of 20% below 1990. Planned policies would bring emissions even further down, but not sufficient yet to meet the conditional pledge of 30% below 1990.

Russia - pledge ambition is rated inadequate and likely to be met: Russia’s BAU emissions are already below the pledged emission level, therefore climate policies no longer affect the likelihood of achieving the target. Existing policies are unambitious in terms of emissions reductions.

India – pledge ambition is rated medium with large data uncertainty and likely to be met: Effort-sharing approaches require no or little deviation from baseline by 2020 and pledge is likely to be achieved even without policy actions. Nevertheless, India has implemented various policies at the national and state level.

Brazil - pledge ambition is rated medium with large data uncertainty and it is not clear if will be met: Although the pledge falls into the ‘sufficient’ category, it is conditional to financial support and is therefore only rated medium. The extremely high share of emissions from land use and land use change (LULUCF) and the high uncertainty for this data makes evaluation of pledge ambition - and if Brazil will meet its target - difficult.

Indonesia - pledge ambition is rated moderate and uncertain if will be met: High uncertainty in emissions from LULUCF in Indonesia makes it difficult to determine the ambition level of the pledge and to what extent policies have an impact on the likelihood of meeting the pledge.

Japan - pledge ambition is rated sufficient but unclear if it will be met: Japan’s energy policy may change significantly as an effect of the Fukushima accident. The policies currently being implemented in Japan may not achieve its relatively ambitious pledge. This is unfortunate, because it threatens to undo Japan’s positive example compared to other developed countries, whose pledges are generally rated inadequate.

Mexico - pledge ambition is rated moderate and unlikely to be met: According to our own detailed country assessment, as well as government sources, Mexico will probably reach only around half of its conditional pledge with currently implemented polices.

Canada - pledge ambition is rated inadequate and unlikely to be met: The pledge does not lead to emission reductions below the 1990 level. Although latest official projections show lower expected future emissions, they still do not meet Canada’s unambitious pledge.

South Korea - pledge ambition is rated sufficient and unclear if it will be met: It is not clear if South Korea will achieve its rather ambitious pledge with current and planned policies. Much will depend on the effective design of the national emissions trading scheme, which South Korea will launch in 2015.

Australia - pledge ambition is rated inadequate and will possibly be met, but the latter is highly uncertain: The unconditional pledge only reflects a reduction of 5% below 2000 levels. Our detailed country assessment last year concluded that this unambitious pledge could be achieved mainly through the Clean Energy Future package. There is significant uncertainty on the effectiveness and continuation of this policy, making a final evaluation difficult.

South Africa - pledge ambition is moderate and unlikely to be met: South Africa’s pledge covers a wide range of emission levels in 2020, referring to uncertainties in the BAU development. Looking at the most recent data, South Africa is currently exceeding its projected BAU emissions. It appears unlikely that with existing or planned policies the country will be able to turn this trend around.

This is a reprinted extract from the publication, ‘2° be or not 2° be’ originally published on

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