Unless the world begins to rapidly reduce greenhouse gas emissions the 1.5C goal of the Paris Agreement “will slip out of reach,” according to the latest UN Environment Programme (UNEP) emissions gap report.
The annual report, now in its 10th year, provides a “bleak” assessment of the ever-growing gap between actual emission reduction commitments by countries and those necessary to achieve the goals of the Paris Agreement: to limit warming to “well-below 2C above preindustrial levels” and pursue efforts to limit the temperature increase to 1.5C.
Global CO2 emissions have increased by around 11% since the first UNEP emissions gap report in 2010. Each year of growing global emissions means that deeper and faster cuts are needed to meet the Paris Agreement targets, and increases the amount of CO2 that would need to be removed from the atmosphere through negative emissions to make the 1.5C target viable.
The 2019 emission gap report suggests that there is no sign of GHG emissions peaking in the next few years. Even if countries meet their existing climate pledges (nationally determined contributions, NDCs) emissions will continue to rise modestly over the next decade, it says. By 2030, the UNEP report estimates that emissions will be 27% and 38% higher than is needed to limit warming to 2C and 1.5C, respectively.
At the same time, there have been some positive developments over the past decade, UNEP notes. Many countries have enacted climate policies, though with differing levels of ambition. Clean energy technologies have fallen in cost as they are deployed at an increasing scale.
This means that while global emissions are still far too high to keep warming well-below 2C, very high emission outcomes with 4C or more warming are also increasingly less likely.
Far from sufficient
UNEP’s annual emission gap report examines the difference between the actions that countries have committed to take and what would be needed to meet agreed-upon climate goals. (Carbon Brief’s archives also include detailed coverage of the UNEP reports in 2014, 2015, 2016, 2017 and 2018.)
The figure below, adapted from the report, shows emission trajectories associated with policies that were in place in 2005 – but nothing after that point – in red and current policies already implemented by governments in orange.
Additional commitments in NDCs that are not yet implemented are shown in yellow for unconditional commitments and light blue for those conditional on aid or action by other countries. Emission trajectories consistent with staying below 2C, 1.8C and avoiding 1.5C are shown in blue, purple and grey, respectively.
Median emission scenarios adapted from figure 3.1 in the UNEP Emission Gap Report 2019. Red line shows a scenario with no new climate policies after 2005, orange shows existing policies already implemented by governments, yellow and light blue lines show additional conditional and unconditional NDCs, blue line shows emissions consistent with a below 2C trajectory, purple line below 1.8C, and grey line shows emissions consistent with a 1.5C trajectory. Chart by Carbon Brief using Highcharts.
There is a large gap between what countries have committed to, in terms of future emission reductions, and what would be needed to meet the Paris Agreement targets. Current NDCs would leave global emissions in 2030 some 12-15bn tonnes of CO2 (GtCO2) short of what is needed to put the world on track to limit warming below 2C, and 29-32GtCO2 short for 1.5C.
While Paris NDCs get the world a small part of the way towards a 2C trajectory, there is no guarantee that even existing Paris commitments will be met, to say nothing of being strengthened. (Countries are due to “communicate or update” their pledges by 2020, under the “ratchet mechanism” of the Paris deal.)
The UNEP report points out that seven large countries are clearly not on track to meet their Paris Agreement commitments: Australia, Brazil, Canada, Japan, South Korea, South Africa and the US.
At the same time, it notes that an increasing number of countries have set net-zero emission targets. Some 65 countries and 10 major regions have committed to net-zero emissions by 2050. However, these only include five members of the G20 group of major economies and only two of these – the UK and France – have passed binding legislation so far.
The 2019 UNEP report features a new 1.8C scenario for the first time, in addition to the below-2C and 1.5C emission trajectories featured in prior reports. This is, in part, because there is a desire to explore outcomes between 1.5C and 2C, as the steady rise in global CO2 emissions puts 1.5C increasingly out of reach.
Time running out for 1.5C
There is relatively little carbon budget remaining for warming to be limited to 1.5C. With 2019 emissions widely expected to be similar to those in 2018, there will be only around 340GtCO2 – or 8 years of current emissions – remaining, that can be emitted before the world passes 1.5C warming.
While this carbon budget can be expanded through the widespread use of negative emissions technologies (NETs) later in the century – as occurs in the 1.5C scenarios used by the UNEP report – there is some reluctance to bet the future on NETs that are largely unproven at scale today.
The figure below, adapted from one created by CICERO’s Dr Robbie Andrews, shows emission trajectories to limit warming to below 1.5C in the absence of net-negative emissions. The different lines show the emissions reductions that would be required if emissions had peaked in each year, between 2000 and 2026, with the current year (2019) highlighted in grey.
Emission reduction trajectories associated with limiting warming below 1.5C by starting year. Solid black line shows historical emissions, while dashed black line shows emissions constant at 2018 levels. Source: Historical CO2 emissions from the Global Carbon Project. 1.5C carbon budgets based on the IPCC SR15 report. Original figure from Robbie Andrews. Chart by Carbon Brief using Highcharts.
If emissions had peaked and begun to decline after the year 2000, the 1.5C target would have been much easier to achieve, only requiring reductions of around 3% per year. By contrast, limiting warming to below 1.5C starting in 2019, without net-negative emissions, would require a 15% cut each year through to 2040.
If emissions continue at current levels for another few years, then the only way to limit warming to below 1.5C in the absence of net-negative emissions would be to immediately cut all global emissions to zero.
Each year that passes without global emission reductions puts the 1.5C target further out of reach. While the below-2C target is easier to achieve than 1.5C, delays will make it increasingly difficult, too. The figure below shows the emission reductions needed, by peaking year, to meet the 2C target without use of net-negative emissions.
Emission reduction trajectories associated with limiting warming below 2C without net-negative emissions, by starting year. Solid black line shows historical emissions, while dashed black line shows emissions constant at 2018 levels. Source: Historical CO2 emissions from the Global Carbon Project. Below-2C carbon budgets based on the IPCC SR15 report. Original figure from Robbie Andrews. Chart by Carbon Brief using Highcharts.
If global emissions had peaked in the year 2000, they would have had to decline at a gradual 1-2% per year to limit warming below 2C by 2100. A more difficult – but still achievable – rate of around 4% to 5% per year would be needed if emissions peak and start to decline after 2019. However, if reductions are delayed for another decade, meeting the 2C target becomes much more challenging, requiring emissions to fall by 7% per year.
Moving away from business as usual
While the UNEP report makes it clear that emissions are far from on track to meet the Paris Agreement goals, it does contain some positive news. The climate policies enacted by countries and the falling price of clean energy technologies have made some of the worst-case emissions outcomes considerably less likely, it says.
The UNEP report projects that current policies will move emissions substantially lower than most of the Intergovernmental Panel on Climate Change (IPCC) scenarios examining potential outcomes in the absence of any action to tackle climate change, so-called “no-policy baseline” pathways.
This follows similar estimates from the 2019 IEA World Energy Outlook, which suggested that stated plans and policies would lead to emissions lower than most IPCC baseline no-policy scenarios over the next few decades.
This is a really important figure. The IEA suggests that falling costs of clean energy make it likely that emissions will be at or below RCP4.5 levels in 2040, even in the absence of any new policies. Its not enough, but it makes worst-case outcomes far less likely (via @jritch) pic.twitter.com/w6nAyMP9bd
— Zeke Hausfather (@hausfath) November 18, 2019
The UNEP report suggests that even if all unconditional NDCs under the Paris Agreement are implemented, the world is still on track for a warming of around 3.2C above pre-industrial levels in the year 2100. While this is far from a desirable outcome, it is substantially better than the 4.6C in the worst-case no-policy emission scenario.