The Intergovernmental Panel on Climate Change’s (IPCC) report on the impacts of global warming provides evidence for why the global community must act to limit global warming to 1.5°C above pre-industrial levels. The report was prepared in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty.

Although targeted towards policymakers, it notes the potential positive impact of directing finance towards investment in infrastructure for mitigation and adaptation. Including mobilising private funds by institutional investors, asset managers and development or investment banks, as well as the provision of public funds.

Understanding Global Warming of 1.5°C

Human activities are estimated to have caused approximately 1.0°C global warming above pre-industrial levels. Warming from the pre-industrial period to the present will persist for centuries to millennia and will continue to cause further long-term changes in the climate system.

These emissions alone (from the pre-industrial period to present) are unlikely to cause global warming of 1.5°C, which is why it is important for the global community to lower emissions sooner rather than later. Future climate-related risks depend on the rate, peak and duration of warming. Reducing and sustaining net zero global anthropogenic (human-caused) CO2 emissions and declining net non-CO2 radiative forcing would halt anthropogenic global warming.

Projected Climate Change, Potential Impacts and Associated Risks

A comparison of scenarios finds that the impact on and risks for each of the following areas are worse at 2°C than at 1.5°C. The areas outlined include:

• Sea level rise
• Biodiversity loss
• Oceans
• Health
• Livelihoods
• Human security
• Food and water
• Economic growth
• Adaptation.

Emissions Pathways and System Transitions Consistent with 1.5°C

The report includes model scenarios and mitigation pathways with differing portfolios. In models with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030, reaching net zero around 2050. For limiting global warming to below 2°C, CO2 emissions are projected to decline by about 25% by 2030 in most pathways and reach net zero around 2070.

Regarding mitigation, pathways limiting global warming to 1.5°C would require rapid and far-reaching transitions in energy, land, urban and infrastructure (including transport and buildings), and industrial systems. Transitions in global and regional land use are found in all pathways, but their scale depends on the pursued mitigation portfolio. Similarly, all pathways include the use of carbon dioxide removal (CDR) over the 21st century.

Strengthening the Global Response

Estimates of global emissions based on current nationally stated ambitions under the Paris Agreement would not limit global warming to 1.5°C. The lower the emissions in 2030, the lower the challenge in limiting global warming to 1.5°C after 2030 with no or limited overshoot. The challenges from delayed actions to reduce greenhouse gas emissions include the risk of cost escalation, lock-in in carbon-emitting infrastructure, stranded assets, and reduced flexibility in future response options in the medium to long term.

The report includes an analysis of the positive and negative effects of mitigation options on each of the sustainable development goals.

1. Global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate.
2. In each model contemplated by this research, the risks and impacts associated with global warming are lower at 1.5°C than at 2°C. These include temperature and sea level rise, impact on biodiversity, ecosystems and species loss, and risks to human health, livelihoods, food security, water supply, human security and economic growth.
3. The challenges from delayed actions to reduce greenhouse gas emissions directly impact upon the financial sector. These challenges include the risk of cost escalation, lock-in in carbon-emitting infrastructure, stranded assets, and reduced flexibility in future response options in the medium to long term.
4. By 2100, global mean sea level rise is projected to be around 0.1 metre lower with global warming of 1.5°C compared to 2°C. A reduction of 0.1 metre in global sea level rise implies that up to 10 million fewer people would be exposed to related risks.
5. Limiting global warming of 1.5°C, compared with 2°C, could reduce the number of people both exposed to climate-related risks and susceptible to poverty by up to several hundred million by 2050.
6. Any increase in global warming is projected to negatively affect human health, including by heat-related morbidity and mortality and vector-borne diseases, such as malaria and dengue fever.
7. Current nationally stated mitigation ambitions submitted under the Paris Agreement would not limit global warming to 1.5°C.
8. Current pathways reflecting nationally stated mitigation ambition until 2030 result in a global warming of about 3°C by 2100, with warming continuing afterwards.
9. The lower the emissions in 2030, the lower the challenge in limiting global warming to 1.5°C after 2030 with no or limited overshoot.
10. Global model pathways limiting global warming to 1.5°C are projected to involve the annual average investment needs in the energy system of around USD$2.4 trillion between 2016 and 2035, representing about 2.5% of the world GDP.