Time to act – the consequences of not limiting global temperature rise to 1.5°C

The Paris Agreement committed the world to limiting global temperature rise to 2°C, with an aspiration of keeping the increase to 1.5°C. Special Report 15 (SR15) of the Intergovernmental Panel on Climate Change (IPCC) considers the likely impacts of global warming of 1.5°C above pre-industrial levels, and the consequences of letting that increase to 2°C.

It looks at possible future global greenhouse gas emission pathways and what might be done to strengthen the worldwide response to the threat of climate change, to keep to those targets.

The IPCC concludes that human activity has already caused approximately 1°C of global warming above pre-industrial levels. At the current rate of increase, global warming is likely to reach 1.5°C between 2030 and 2052. Put in simple terms, warming is happening fast, and there is real urgency if we are to limit the global temperature rise to just 1.5°C.

The IPCC concludes that, if we stopped anthropogenic (human-made) carbon emissions now, we would be unlikely to breach the 1.5°C limit – but we are nowhere near that point. It will require us to achieve, and sustain, net-zero global anthropogenic CO₂ emissions to halt global warming for the long term.

We also need to reduce, or eliminate, emissions of the other greenhouse gases, including methane, aerosols, F-Gases, nitrous oxide and sulphur dioxide.

SR15 says the climate models now project robust differences in regional climate characteristics between current conditions, global warming of 1.5°C, and warming to between 1.5°C and 2°C. These differences include higher mean temperature in most land and ocean regions, hot extremes in most inhabited regions, a real prospect of heavy precipitation, and the probability of drought and precipitation deficits in some regions. It is becoming clear that holding the line at 1.5°C will make a genuine difference to future conditions.

Not just about climate

Climate-related risks to health, livelihoods, food security, water supply, human security and economic growth increase with global warming of 1.5°C, and will grow further with a 2°C rise. This has significant and immediate implications for national policies, and for our work as building services engineers. If we accept the need to achieve net-zero emissions, and fast, we must make significant reductions in emissions from our building stock – and fast. Far more must be done to cut emissions from existing buildings. Transport-related emissions must be cut fast, driving a switch to electric vehicles and the charging infrastructure they need. This challenge is global, requiring a global response. As a worldwide body, CIBSE has a key role to play in that response.

In Australia last month, the government lost the seat vacated by former prime minister Malcolm Turnbull on a 28% swing, to an independent candidate campaigning for more action on climate change. Even in the US, while the federal government no longer supports the Paris Agreement, states and cities are redoubling their efforts to cut emissions.

The UK has already seen a hardening of view by the independent Committee on Climate Change, which – in June – called on the government to do more to meet the current legal target of an 80% reduction in emissions by 2050. SR15 drives that call home hard. The forthcoming review of Part L in England needs to take SR15 seriously.

We know the real challenge is to cut emissions from existing buildings – a tough problem to solve. But SR15 demands that we redouble our efforts and take much more urgent action. Given the time it takes to discuss and agree changes to regulations and standards, implement them, and then start building to them, we have no time to lose.

The message from the IPCC is clear. Time is running out to prevent a global temperature rise of more than 1.5°C. The consequences of a 2°C rise are likely to be significantly worse. This is our chance to have an impact on the world. It is time to act.

Dr Hywel Davies is technical director at CIBSE