Climate change: experts warn over “glaring and growing gap” between targets and reality

The world’s leading climate science organizations have joined forces to produce a landmark new report for the United Nations Climate Action Summit, underlining the glaring – and growing – gap between agreed targets to tackle global warming and the actual reality.

The report, United in Science, includes details on the state of the climate and presents trends in the emissions and atmospheric concentrations of the main greenhouse gases. It highlights the urgency of fundamental socio-economic transformation in key sectors such as land use and energy in order to avert dangerous global temperature increase with potentially irreversible impacts.

The report is warning that levels of the main long-lived greenhouse gases, carbon dioxide (CO2), methane (CH4)) and nitrous oxide (N2O) have reached new highs.

Globally carbon dioxide emissions grew 2% and reached a record high of 37 billion tonnes of CO2 in 2018. There is still no sign of a peak in global emissions, even though they are growing slower than the global economy.

“The Report provides a unified assessment of the state of our Earth system under the increasing influence of anthropogenic climate change, of humanity’s response thus far and of the far-reaching changes that science projects for our global climate in the future. The scientific data and findings presented in the report represent the very latest authoritative information on these topics,” said the Science Advisory Group to the UN Secretary-General’s Climate Action Summit.

“It highlights the urgent need for the development of concrete actions that halt the worst effects of climate change.”

Highlights from the report include:

Record greenhouse gas concentrations in the atmosphere

Levels of the main long-lived greenhouse gases, carbon dioxide (CO2), methane (CH4)) and nitrous oxide (N2O) have reached new highs.

The last time Earth’s atmosphere contained 400 parts per million CO2 was about 3-5 million years ago, when global mean surface temperatures were 2-3°C warmer than today, ice sheets in Greenland and West Antarctica melted, parts of East Antarctica ice had retreated, all causing global see level rise of 10-20m compared with today.

In 2018, global CO2 concentration was 407.8 parts per million (ppm), 2.2 ppm higher than 2017. Preliminary data from a subset of greenhouse gas monitoring sites for 2019 indicate that CO2 concentrations are on track to reach or even exceed 410 parts per million (ppm) by the end of 2019.

In 2017, globally averaged atmospheric concentrations of CO2 were 405.6 ±0.1 ppm, CH4) at 1859 ±2 parts per billion (ppb) and N2O at 329.9 ±0.1 ppb. These values constitute, respectively, 146%, 257% and 122% of pre-industrial levels (pre-1750).

The growth rate of CO2 averaged over three consecutive decades (1985–1995, 1995–2005 and 2005–2015) increased from 1.42 ppm/yr to 1.86 ppm/yr and to 2.06 ppm/yr

Warmest five-year period on record

The average global temperature for 2015–2019 is on track to be the warmest of any equivalent period on record. It is currently estimated to be 1.1°Celsius (± 0.1°C) above pre-industrial (1850–1900) times. Widespread and long-lasting heatwaves, record-breaking fires and other devastating events such as tropical cyclones, floods and drought have had major impacts on socio-economic development and the environment.

Continued decrease of sea ice and ice mass

Arctic summer sea-ice extent has declined at a rate of approximately 12% per decade during 1979-2018. The four lowest values for winter sea-ice extent occurred between 2015 and 2019.

Overall, the amount of ice lost annually from the Antarctic ice sheet increased at least six-fold between 1979 and 2017.  Glacier mass loss for 2015-2019 is the highest for any five-year period on record.

Sea-level rise is accelerating, sea water is becoming more acidic

The observed rate of global mean sea-level rise accelerated from 3.04 millimeters per year (mm/yr) during the period 1997–2006 to approximately 4mm/yr during the period 2007–2016. This is due to the increased rate of ocean warming and melting of the Greenland and West Antarctica ice sheets. There has been an overall increase of 26% in ocean acidity since the beginning of the industrial era.

Global carbon budget

Carbon dioxide emissions grew 2% and reached a record high of 37 billion tonnes of CO2 in 2018. There is still no sign of a peak in global emissions, even though they are growing slower than the global economy.

Current economic and energy trends suggest that emissions will be at least as high in 2019 as in 2018. Global GDP is expected to grow at 3.2% in 2019, and if the global economy decarbonized at the same rate as in the last 10 years, that would still lead to an increase in global emissions.

Despite extraordinary growth in renewable fuels over the past decade, the global energy system is still dominated by fossil fuel sources. The annual increase in global energy use is greater than the increase in renewable energy, meaning the fossil fuel use continues to grow. This growth needs to halt immediately.

The net-zero emissions needed to stabilize the climate requires both an acceleration in use of non-carbon energy sources and a rapid decline in the global share of fossil fuels in the energy mix. This dual requirement illustrates the scale of the challenge.

Natural CO2 sinks, such as vegetation and oceans, which remove about half of all emissions from human activities, will become less efficient at doing so. This underscores the need to reduce deforestation and expand natural CO2 sinks, particularly those in forests and soils that can be improved by better management and habitat restoration.

The emissions gap – where we are and where we need to be

The UNEP Emissions Gap Reports, with the tenth edition being published this November, assess the latest scientific studies on current and estimated future greenhouse gas emissions; they compare these with the emission levels permissible for the world to progress on a least-cost pathway to achieve the goals of the Paris Agreement. This difference between “where we are likely to be and where we need to be” is known as the emissions gap.

Global emissions are not estimated to peak by 2030, let alone by 2020, if current climate policies and ambition levels of the Nationally Determined Contributions (NDCs) are maintained. Preliminary findings from the Emissions Gap Report 2019 indicate that greenhouse gas emissions continued to rise in 2018.

The emissions gap in 2030 between emission levels under full implementation of conditional Nationally Determined Contributions (NDCs) and levels consistent with least-cost pathways to the 2°C target is 13 GtCO2e. If just the unconditional NDCs are implemented, the gap increases to 15 GtCO2e. The gap in the case of the 1.5°C target and 2°C target is 29 GtCO2e and 32 GtCO2e respectively.

Current NDCs are estimated to lower global emissions in 2030 by up to 6 GtCO2e compared to a continuation of current policies. This level of ambition needs to be roughly tripled to align with the 2°C limit and must be increased around fivefold to align with the 1.5°C limit.

Implementing unconditional NDCs, and assuming that climate action continues consistently throughout the twenty-first century, would lead to a global mean temperature rise between 2.9°C and 3.4°C by 2100 relative to pre-industrial levels.

If NDC ambitions are not increased immediately and backed up by action, the scientists are warning that exceeding the 1.5°C goal can no longer be avoided. If the emissions gap is not closed by 2030, it is very plausible that the goal of a well-below 2°C temperature increase is also out of reach.