AVOIDing dangerous climate change

AVOID title

March 2013 - The AVOID programme for researching dangerous climate change held its final symposium on the 12 February at the Royal Society in London. Over ninety high-level delegates from across government, academia, research bodies and business attended the event to see the programme's results and discuss the implications for policy and society. The background to the AVOID programme and a few of the research highlights presented at the final symposium are described here.

Introduction to the AVOID research programme

The concept of avoiding 'dangerous' climate change was set out in the Convention on Climate Change adopted at the Rio Earth Summit in 1992. It aims to achieve the  "...stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner."  The "Avoiding Dangerous Climate Change (AVOID)" programme was established in 2009 to provide advice to the UK Government on avoiding levels of global greenhouse gas emissions that cause potentially dangerous climate change. From the outset of the AVOID programme, the scientific research was focused on three questions:  

  • What are the characteristics of potentially dangerous climate change?  
  • What greenhouse gas emissions pathways will avoid 'dangerous' climate change?  
  • What is the feasibility of such pathways?

The AVOID programme has studied the basis for and implications of a range of climate targets, and potentially dangerous regional impacts and feasible emissions reductions more generally.  

The research was funded by the UK Government's Department of Energy and Climate Change (DECC) and Department for Environment, Food and Rural Affairs (Defra), and is one of the Living With Environmental Change accredited activities. AVOID programme research was conducted by a multi-disciplinary network of scientists at the Met Office Hadley Centre, Walker Institute at the University of Reading, Grantham Institute for Climate Change at Imperial College and the Tyndall Centre through the University of East Anglia, along with other national and international collaborators.  

AVOID's work is considered successful and effective because policy focused questions informed research priorities, allowing timely and relevant research to be delivered on key topics. This was achieved by the unique approach adopted by the AVOID programme; Government stakeholders, involved from the earliest stages, maintained direct communication with researchers, ensuring research priorities and timescales remained aligned with policy needs. The researchers were also able to draw on more detailed and in depth research programmes focussing their results on the policy questions. The AVOID programme has also engaged with stakeholders in China, India and the USA.  

Greenhouse gas emissions compatible with limiting warming to 2 °C  

Greenhouse gas emissions pathways for the year annual emissions peak Figure 1: Greenhouse gas emissions pathways for the year annual emissions peak (x-axis), subsequent percentage reduction rate (y-axis) and amount of negative emissions required (coloured dots) to limit global temperature rise in the 21st century to 2 °C (+/- 0.1 °C) above pre-industrial with a 50% chance in this study.

  • The 2 °C warming limit is achievable with a 50% chance with a peak in emissions in the next few years followed by rapid long-term reductions in emissions. 
  • The later emissions peak, the more likely that techniques to remove carbon dioxide from the atmosphere will need to be developed and employed to limit warming to 2 °C. 

The AVOID programme generated a large set of future emissions pathways (annual emissions to 2100) varying the year in which emissions start to fall, the subsequent reduction rate and long-term stabilisation level. Some pathways assumed that later this century greenhouse gases could be extracted from the atmosphere with a future negative emissions technology. Temperature levels were deduced from a climate model.  

Figure 1 shows emissions pathways with a 50% chance of limiting 21st century global warming to about 2 °C above pre-industrial levels. It illustrates that meeting the 2 °C target is feasible but challenging. For example, a pathway peaking by 2015 has an even chance of limiting warming to 2 °C if emissions then fall by about 3% per year and without any negative emissions technology. For pathways in which emissions peak later (green, orange and red dots), global temperature rise can only be limited to 2 °C with reduced emissions from fossil fuel and land use change, and the deployment of negative emissions sources. Earlier peak years relax the reduction rate required to meet the target.  

AVOID also found, in another study, that deforestation and other land-use changes make up about 10% of current global emissions. Reducing global emissions without tackling land-use change emissions, in particular from tropical deforestation, will make keeping below the 2 °C target even less likely.    

Feasibility of emissions reductions 

Emissions savings in China's energy end-use sectors in 2050 Figure 2: Emissions savings in China's energy end-use sectors in 2050, compared to a business-as-usual for 2050 Baseline case.

  • The transition to a low carbon economy, which is necessary to limit warming, appears challenging but is still technologically and economically feasible. 
  • This transition would require a combination of decarbonisation of the industrial, transport and buildings sectors and energy efficiency measures. 

Several AVOID studies have assessed the global and regional technology options and costs associated with long-term low-carbon pathways. A comparison of integrated assessment models showed that the transition to a global low-carbon economy by 2050 (which is broadly consistent with the 2 °C goal) is possible, but estimated costs of mitigation vary widely, depending on the modelling and data assumptions made. Negative emissions technologies are likely to be important but key practical challenges remain. 

Region-specific analyses of China and India showed that they could in theory achieve and even exceed their 2020 Copenhagen Accord pledges. To do so they must realise a wide range of low or negative cost energy efficiency measures across their power, industrial, building and transport sectors, as well as promoting lower-carbon power sources such as wind, hydro and nuclear. Longer-term, to reach very low emissions levels in 2050, these economies would likely need near-decarbonised power sectors, considerable cross-sector electrification, and almost all available energy efficiency, and other options as shown for the example of China in Figure 2. Such a transition could cost of the order 1-2% of GDP per year by 2050. 

These technology transitions set a challenging research, development and deployment agenda, which will require a wide range of policies to deliver new energy technologies and make energy efficiency savings.   

Results: impacts avoided by reducing greenhouse gas emissions

  • Climate mitigation policy that limits 21st century global warming to 2 °C avoids significant harmful climate impacts. 
  • Tough limits on global emissions of greenhouse gases could avoid 20 to 65% of the damaging effects of climate change by 2100 relative to a business-as-usual pathway which reaches 4 °C by 2100. 

The 2 °C policy target is based on global temperature, but the consequences of climate change are felt and managed at a much smaller scale. AVOID has investigated the impacts of climate change for 12 indicators on a global grid and combined them into sub-continental scale regions. It used spatial patterns of climate change from climate models. 

Figure 3 shows examples of the substantial variation of impacts avoided between sectors. It compares impacts resulting from business-as-usual emissions pathways (leading to a 4 to 5.5 °C temperature rise by 2100) with an emissions pathway with a 50% chance of limiting 21st century global surface temperature rise to 2 °C above pre-industrial levels. 

Even by 2050 a 2 °C climate mitigation policy has avoided 30% of exposure to river flood frequency (relative to a 4 °C business-as-usual future or about 50% relative to a 5.5 °C business-as-usual case). The benefits of climate mitigation policy to water resources stress are smaller, reducing it by 5 to 8% by 2050. This is because even a small amount of warming can alter rainfall patterns sufficiently to reduce water availability. Most sectors benefit significantly from climate mitigation, but some could experience disadvantages; the climate change benefits of reduced exposure to river flood and drought, and energy savings from heating buildings, are lessened by climate policy (see Figure 3).  

Range of estimated global impacts avoided and benefits lost Figure 3: Range of estimated global impacts avoided and benefits lost, of an emissions pathway with a 50% chance of limiting warming to 2 °C, relative to business-as-usual emissions pathways which lead to between 4 °C and 5.5 °C by 2100.

The impacts avoided by 2100 are generally much greater than those avoided by 2050 above. Tough limits on global emissions of greenhouse gases could avoid 20 to 65% of the damaging effects of climate change by 2100 relative to a business-as-usual pathway which reaches 4 °C by 2100. 

In an AVOID programme study on biodiversity impacts, a partial assessment of European biodiversity projected an 80% reduction in the number of plant and mammal species becoming endangered in status, if warming can be limited to 2 °C by comparison to 4 °C warming. 

Further AVOID research has focused on economic impacts, based on the same mitigation scenarios, and revealed the benefits of stringent mitigation measured in global aggregate economic terms. It used an integrated assessment model and found that if emissions peak globally in 2016, around half of the business-as usual impacts can be avoided by 2080. If mitigation is delayed so that emissions peak in 2030, only around a third of the impacts can be avoided. 

The studies on impacts found that although not all impacts can be avoided by limiting warming to a 2 °C pathway, mitigation also postpones the decade in which a given level of climate change impacts is projected to occur. Hence the mitigation would allow further time for adaptation to take place.  

Reports, posters, presentations and briefings are available from the AVOID website.

Last updated: 14 August 2014