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On October 8, the IPCC Special Report on 1.5°C (IPCC-SR1.5) was published in the Republic of Korea, by the IPCC – a global body of climate scientists.

This report is considered to be one of the most important scientific studies on climate change in the last decades, and it will determine how we deal with climate change in the coming years.

Here we explain the take-away messages from the IPCC SR1.5 report in 7 questions and answers:

Why are we talking about 1.5°C?

Climate change represents an urgent and potentially irreversible threat to human societies and the planet. In recognition of this, the overwhelming majority of countries around the world adopted the Paris Agreement in December 2015, the central aim of which includes pursuing efforts to limit global temperature rise to 1.5°C.

In doing so, these countries, through the United Nations Framework Convention on Climate Change (UNFCCC) also invited the IPCC – a global body of climate scientists – to provide a Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emissions pathways.

How close are we to 1.5°C?

Human-induced warming has already reached about 1°C above pre-industrial levels at the time of writing of this Special Report. By the decade 2006–2015, human activity had warmed the world by 0.87°C (±0.12°C) compared pre-industrial times (1850–1900).

If the current warming rate continues, the world would reach human–induced global warming of 1.5°C around 2040.

How do we limit global warming to 1,5°C? And will we make it?

There is no definitive, single, way to limit global temperature rise to 1.5°C above pre-industrial levels. This Special Report is broadly looking at 2 different scenarios:  One scenario keeps global temperature at, or just below, 1.5°C. Another sees global temperature temporarily exceed 1.5°C ( this is referred to as an overshoot) before coming back down. Countries’ pledges to reduce their emissions are currently not in line with limiting global warming to 1.5°C. The two types of pathway have different implications for greenhouse gas emissions, as well as for climate change impacts and for achieving sustainable development.

All of the scenario’s used in the Special Report on 1.5°C show that current pledges are not on track to limit global warming to 1.5°C above pre-industrial levels.

If current national pledges for 2030 are achieved but no more, researchers find very few (if any) ways to reduce emissions after 2030 sufficiently quickly to limit warming to 1.5°C.

A world that is consistent with holding warming to 1.5°C would see greenhouse gas emissions rapidly decline in the coming decade, with strong international cooperation and a scaling up of countries’ combined ambition beyond current NDCs.

How can we can limit warming to 1.5°C?

Limiting global warming to 1.5°C above pre-industrial levels would require major reductions in greenhouse gas emissions in all sectors, the IPCC report confirms. But different sectors are not independent of each other and making changes in one can have implications for another. For example, if we as a society use a lot of energy, then this could mean we have less flexibility in the choice of mitigation options available to limit warming to 1.5°C. If we use less energy, the choice of possible actions is greater. For example we could be less reliant on technologies that remove carbon dioxide (CO2) from the atmosphere.

Warming will not be limited to 1.5°C or 2°C unless emissions decline rapidly across all of society’s main sectors, including buildings, industry, transport, energy, and agriculture, forestry and other land use. Actions that can reduce emissions include, for example, phasing out coal in the energy sector, increasing the amount of energy produced from renewable sources, electrifying transport, and reducing the ‘carbon footprint’ of the food we consume.

What are the impacts of 1.5°C and 2°C of warming?

The report confirms that the impacts of climate change are already being felt in every inhabited continent and in the oceans. But they are not spread uniformly across the globe, and different parts of the world experience impacts differently.

An average warming of 1.5°C across the whole globe raises the risk of heatwaves and heavy rainfall events, amongst many other potential impacts. Limiting warming to 1.5°C rather than 2°C can help reduce these risks. But the impacts the world experiences will depend on the specific greenhouse gas emission ‘pathway’ taken. The consequences of temporarily overshooting 1.5°C and returning later in the century, for example, could be larger than if temperature stabilizes below 1.5°C. The size and duration of an overshoot will also affect future impacts.

What is Carbon Dioxide Removal?

Carbon Dioxide Removal (CDR) refers to the process of removing CO2 from the atmosphere.

Since this is the opposite of emissions, practices or technologies that remove CO2 are often described as achieving ‘negative emissions’. The process is sometimes referred to more broadly as Greenhouse Gas Removal if it involves removing gases other than CO2.

There are two main types of CDR: either enhancing existing natural processes that remove carbon from the atmosphere (e.g., by increasing its uptake by trees, soil, or other ‘carbon sinks’) or using chemical processes to, for example, capture CO2 directly from the ambient air and storing it elsewhere (i.e., underground). All CDR methods are at different stages of development and some are more conceptual than others, as they have not been tested at scale.

Almost all current climate models in the IPCC SR1.5 assume the use of some form of CDR in the future to limit global warming.

Why is adaptation important in a 1.5°C warmer world?

Adaptation is the adjustment process to current or expected changes in climate and its effects.

Even though climate change is a global problem, its impacts are experienced differently across the world. This means that responses are often specific to the local context, and so people in different regions are adapting in different ways.

A rise in global temperature from 1°C to 1.5°C, and beyond, increases the need for adaptation. Therefore, stabilising global temperatures at 1.5°C above pre-industrial levels would require a smaller adaptation effort than for 2°C. Despite many successful examples around the world, progress in adaptation is, in many regions, in its infancy and unevenly distributed globally.

Arthur Wyns

About Arthur Wyns

Arthur Wyns is a tropical biologist and science journalist who writes about climate change, environment and migration. He manages Programs and Partnerships for Climate Tracker since 2017.