Are we on track to limit global warming to 1.5°C above the pre-industrial level?

Figure 1. Two main pathways for limiting global temperature rise to 1.5°C above pre-industrial levels are discussed in IPCC’s Special Report. The pathways are: stabilizing global temperature at, or just below, 1.5°C (left) and global temperature temporarily exceeding 1.5°C before coming back down later in the century (right). Temperatures shown are relative to pre-industrial but pathways are illustrative only, demonstrating conceptual not quantitative characteristics. Source: IPCC Special Report 15 (2014).

Introduction – defining pathways to the future

To determine what it takes to limit global temperature rise to 1.5°C above pre-industrial levels scientists have defined different pathways. The IPCC Special Report 15 (2014) identifies two main conceptual pathways: One where the global temperature is stabilized just below 1.5°C, and one where global temperature exceed 1.5°C for a while before coming back down, as illustrated above.

So how do we get to these two pathways?

The future is something we can only predict, therefore scientists use models to simulate the effects of greenhouse gas emissions on the future levels of warming. Simulations

with different amounts and intensities of greenhouse gas emissions result in different levels of warming. Each simulation describes a future possible pathway. There are many different pathways that can limit the warming to below 1.5°C.

The two pathways identified by IPCC have different implications on how much greenhouse gases we can emit, and how these emissions will impact the climate as well as sustainable development. The second pathway in the illustration above overshoots the target of 1.5°C for some time. The longer this overshoot is the more we have to rely on techniques that can actively remove CO2 from the atmosphere, in combination with reduced emissions. This is referred to as climate engineering, or geo-engineering, which is something we will address in a future post here at The Environmentalization.

What are we doing to meet the target to keep the warming under 1.5°C?

All countries that have formally accepted the Paris Agreement have to pledge how they will address climate change. At Climate Home News you can read more about what some countries have committed to do. Currently, however the combined effect of all the pledges that have been made are not enough to limit global warming to 1.5°C above preindustrial levels. This means that warming will exceed 1.5°C, for at least a period of time. As mentioned above, this pathway requires geo-engineering to remove CO2 from the atmosphere in combination with extensive reduction of greenhouse gas emissions to return warming to 1.5°C at a later stage.

So, which of the two pathways is the most likely one?

The answer to this question depends on how much each country manages to reduce its greenhouse gas emissions. We have learnt that the current pledges are not enough. Based on the level of commitment required (e.g. transition from fossil based energy system to one based on renewable energy, less flight travels, reduce consumption, less plastics, reduce meat production etc.) to reduce our greenhouse gas emissions, we can expect delayed action, limited international cooperation, and insufficient policies, leading to stagnating or increasing greenhouse gas emissions, preventing us from making the target of 1.5°C above pre-industrial levels. In other words: we should prepare for a situation when the global average temperature exceeds 1.5°C above the pre-industrial level.


  • Many countries have made pledges to reduce CO2 emissions but it is not enough to keep the warming under 1.5°C.
  • We will most likely experience an overshoot when the global warming exceeds 1.5°C for a time
  • The impacts of a global warming above 1.5°C are uncertain and may even result in the climate exceeding a tipping point, i.e. a threshold that, when exceeded, can lead to large changes in the state of the system
  • To reduce the global average temperature when it increased more than 1.5°C we have to apply practices and techniques of geo-engineering in combination with extensive reduction of our greenhouse gas emissions
  • Geo-engineering at this scale has never been tested


This text is a reflection based on the Frequently Asked Questions (FAQ2.1) extracted from chapter 1 of IPCC’s fifth assessment report.

You can download the entire FAQ document here: IPCC Special Report 15, 2014

You can read more about what different countries have pledged to address climate change in the post: Which countries have a net zero carbon goal? published 14 June 2019 at Climate Change Home

How come that an increase of the global average temperature of 1.5°C has such enormous effects on life on earth?

When I think about global warming I sometimes think about the temperature of the human body. When it is healthy the body temperature ranges between 36.5–37.5 °C. A temperature above 37.5°C is referred to as a fewer, signalling that the body isn’t well. An increase by 1.5°C would equal a body temperature between 38-39°C, which is clearly defined as a fewer. We all know how a fewer affects us. You are tired, maybe having some muscle pains and you are not able to perform at your best. The higher the fever the worse it gets. As just a little increase of body temperature has such profound effects on our abilities, it might make it easier to understand that an increase of 1.5°C is like our planet having a fever and that is doesn’t function at its best.

This comparison just illustrates how an increase in human body temperature of 1.5°C is perceived by us humans. It doesn’t explain why the effects of such a small increase of the global average temperature is such a big issue. The explanation lies in the term average. It doesn’t mean that the temperature will be 1.5°C everywhere, only that the average of all temperatures on earth equals an increase of 1.5°C relative to the pre-industrial times. It doesn’t say anything about the deviations from the average. What we know is that land masses warm more than the oceans, and that some parts of earth warm more than others. This suggests that some parts of earth is running a far higher fewer than what the average temperature suggests. These larger temperature differences influence weather systems, resulting in more intense storms, with record breaking wind speeds and extreme precipitation. Other parts of earth see prolonged droughts leading to lost harvests and starvation of humans and animals. Again, these extreme weather situations together with rising sea levels and a generally warmer climate will force people to leave the areas which become inhabitable. The number of climate migrants will most likely outnumber the current wave of migrants seeking refuge in Europe and elsewhere by far.

According to IPCC we will already in 2040 have reached a global average temperature that is 1.5°C above the pre-industrial level. This is in just 21 years! This clearly signals that we have no time to spare and urgent actions are required if we want to halt the global warming. To do this:

  1. We all have to contribute to drastically reduce our GHG emissions into the atmosphere.
  2. We can’t afford to carry on with business as usual for much longer, waiting for someone else to fix this problem, it is everyone’s responsibility to take action.

The text is a reflection based on the Frequently Asked Questions (FAQ1.2) extracted from chapter 1 of IPCC’s fifth assessment report.

You can download the entire FAQ document here.

Why is 1.5°C so important?

Illustration from FAQ1.2, summary of FAQs in IPCC AR5

At the decade 2006-2015, human activity had caused the global average temperature had increased by 0.87°C (+/-0.12°C) compared to pre-industrial times (1850-1900).

In 2015 a majority of the counties in the world gathered in Paris to discuss what to do with the climate crisis. The outcome of this meeting organized by the United Nations Framework Convention to Combat Climate Change (UNFCCC) was a commitment to limit global temperature rise to 1.5°C. So, the question is, why did the countries decide on a limit of global temperature rise of 1.5°C?

The actual agreement stated: ‘holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuit efforts to limit the temperature increase to 1.5°C above pre-industrial levels’.

An extensive review of the long-term global goals conducted by experts and representatives from UNFCCC concluded that in some vulnerable ecosystems, high risks are projected even at a warming of 1.5°C. This led to the decision to not stop at 2°C as the defense line, but to strive towards a goal of keeping the temperature increase to below 1.5°C.

A key reason for a lower limit is that already at an increase of global average temperature with 1.5°C from pre-industrial levels the expected impacts are so extensive that there is a limited capacity to adapt to its impacts. This is particularly the case in developing and island countries.

This is why limiting the increase of global average temperature to less than 1.5°C is so important, a majority of developing and island nations will not be able to cope with the changed conditions that this warming will bring. The effect of these countries not coping is likely to be massive migration from these nations, to areas less affected by the direct impacts of climate change.


The text is a reflection based on the Frequently Asked Questions (FAQ1.2) extracted from chapter 1 of IPCC’s fifth assessment report.

You can download the entire FAQ document here.

The urgency of the climate crisis – but there is (little) hope on the way

Most of us have heard about climate change caused by anthropogenic (man-made) greenhouse gas emissions (GHG) and the effects that a further increase of the global temperature from today 0.99°C to 1.5°C, 2°C and beyond will have for all mankind. What we haven’t sufficiently realised is how dangerous the game that we are playing really is and how urgent drastic changes are required to minimise the risk of so-called tipping points. Tipping points are critical thresholds that once they are reached will lead to abrupt and irreversible changes of the ecosystem. The release of carbon dioxide and other GHGs can lead to such tipping points due to their impact on the global atmospheric temperature and as a consequence avoiding the release of GHGs to the atmosphere is the necessary step to stay as far as possible away from the critical thresholds.

The carbon dioxide budget is the best concept to visualise how serious the current situation is. In order to stay below 1.5°C global warming that all nations in 2015, with the Paris Climate Agreement preferably agreed on, we have with our current emissions (1,331 tons of CO2 per second) a budget of 361,538,000,000 tons left. This corresponds to a time period of 8 years, 7 months and 7 days, assuming that the emissions are remaining constant. If we look at the numbers with the 2°C scenario that all nations with the Paris Climate Agreement definitely agreed on we have 26 years, 5 months and 15 days left. A live carbon clock can be found at the Mercator Research Institute on Global Commons and Climate Change (MCC) webpage.

Considering our current global consumption of and dependence on fossil fuels and the speed of political decisions, especially on a global scale, both 8 and 26 years will not be enough to keep global warming under the accepted limits. But today, initiated by the movement FridaysForFuture, people all over the world (in 1,623 places in 119 countries) are protesting against the lack of action on the climate crisis. That people on a large scale realise the urgency of the climate crisis and and are willing to fight for action, is giving a spark of hope that we can still change tack. In this matter, every voice and every contribution counts. Let’s start together.

4,962 strikes in 1,623 places in 119 countries on the 24th of May 2019.

First steps towards an environmental blog, the Environmentalization

This blog is the product of our expanding portfolio of on-line courses in environmental engineering at Malardalen University in Sweden.

We are currently offering a range of courses on undergraduate and graduate levels, ranging from Introduction to environmental engineering to energy and natural resources, energy and climate, all on undergraduate level. On advanced level we offer courses in air quality management, biomass to energy, waste water management as well as short courses on circular economy, humanitarian engineering and sustainable consumption.

You can read more about the advanced level on-line courses here.

As the number of students applying to these courses increase, and we have created a rather large group of students that have taken our courses, we identified a need for a platform where we can exchange information and engage in discussions outside the formal course environment, involving students and practitioners in the field to keep in contact and to contribute to life long learning.

The focus of this site is on the subject of environmental engineering but touching on relevant aspects of energy systems and social sciences, as well as current affairs, as all these influence our environment. A special attention is given to the increasing levels of greenhouse gases in the atmosphere and their impact on the global climate. We see this as one of our times biggest challenges and would therefore like to share information and knowledge about this, and by doing so, contribute to a better understand of what the issues are and what we can do about them, both as individuals and a society.

We hope you will find this site interesting and that it will bring you some new insights into the exciting world of environmental engineering and sustainable development.