Despite climate action so far, annual emissions of global-warming greenhouse gases (GHGs) continue to rise - more rapidly than in the decade before, 2000 to 2010.

About half of historical cumulative greenhouse gas (GHG) emissions have occurred in the last 40 years. One has to ask: how can this be? Where is the growth in emissions coming from? As part of one of three working groups contributing to the IPCC's fifth assessment report on mitigation, 235 experts overseen by 38 review editors assessed nearly 10 000 publications to find answers.

As it turns out, three quarters of the growth in GHG emissions is from energy supply and industry - much of this from fossil fuel combustion, cement production, and flaring. Two key drivers of these emissions are economic growth, and - to about roughly half the extent - population growth. Simply put, the problem of emissions growth is due to the affluent population. Most worryingly, the trend of gradual decarbonisation of energy supply from 1970 to 2000 has been reversed; and the carbon intensity of energy has increased from 2000 to 2010, due to more coal being used. The efforts to improve energy efficiency and find alternative energy options are being outweighed by the opposite trend: we (as a planet) have been burning dirtier fuels (coal and oil), and lots more of them!

High-income countries (the IPCC's report on mitigation uses World Bank country classification by gross national income per capita) are responsible for disproportionately large per capita emissions. The poorer half of these countries emit more than six times the per capita emissions of the poorer half of the lower-income countries. Within the income groups there is glaring inequality in per capita emissions between the poorest and the richest, especially in high- and lower-income countries. However, emissions per capita in upper-middle income countries are increasing - pointing to the carbon footprint of the global middle class, including in South Africa. The report points out that upper- and lower-middle-income country emissions are in part for products exported to, and consumed, in high-income countries. The trend of growing emissions means we are way off track in limiting global warming to 2°C above pre-industrial levels, let alone strengthening that politically agreed goal to 1.5°C. Without increased mitigation, current emission trends put us on a path to 3.7° to 4.8°C above by the end of this century. Even assuming the climate action described in the Cancún Pledges - if extended at that low level of ambition into the future - average global temperature increase above pre-industrial levels is likely to near 3°C. Clearly, more and urgent action is needed.

We need to decarbonise electricity far faster than we have, in all sectors of society: government, industry, business, and individuals - and, most urgently, the high emitters. Improving energy efficiency and reducing energy demand is important, but is not enough on its own. Low and zero-carbon technologies play an essential role in climate-change mitigation. Negative carbon technologies - such as bio-energy with carbon capture and storages (BECCS) - will be a critical component of a global emissions pathway to warming levels within 2°C above pre-industrial levels. Decarbonisation requires large changes in investment patterns - a 20% decline in carbon-intensive sectors, and double the past levels of investment in low-carbon energy. Renewable energy technologies are maturing; we need to scale up deployment rapidly, as these are the most sustainable resource alternatives. Co-benefits, such as improved air quality, further offset the cost to society of shifting investment. Technology and investment form part of the plan; but the most instantly implementable mitigation option is that of behaviour. Behaviour change is the most cost-effective (and equitable) mitigation option, and it is essential for reducing energy demand and emissions without compromising development.

UCT Professor Harald Winkler, assisted by Samantha Keen, and Professor Dave Dewar joined authors and expert reviewers from more than 55 countries in assessing scientific, technological and socio-economic literature relevant to tackling climate change for the Intergovernmental Panel on Climate Change's fifth report, 'Climate Change 2014: Mitigation of Climate Change'. Key findings of the Working Group III's contribution to the IPCC 5th Assessment Report (AR5) were presented at a public seminar hosted by the Energy Research Centre on 14 April, the day after its release in Berlin. The evening was well attended, and the audience heard responses to the report from government, business and civil society. This event followed the African Climate and Development Initiative open discussion meeting on 2 April, where key insights and challenges were shared from the IPCC Working Group II's contribution to AR5, 'Climate Change 2014: Impacts, Adaptation and Vulnerability'.

Harald Winkler & Samantha Keen, Energy Research Centre.