Sebastian Mernild, our former director and now pro-rector and professor in climate change and glaciology at the University of Southern Denmark and in an adjunct position with us, is one of the Lead Authors contributing to the report!

Extreme weather events indicate climate change is here

The climate of our planet is changing, and more and more evidence points at us humans as the culprit. According to the IPCC report published today, we caused almost the entirety of global warming in the past decade (2011-2020), compared to the average temperature between 1850 and 1900: It was 1,09 °C warmer, and it is very likely that human activity influencing the climate was responsible for 1,07 °C of that! We pump too much CO₂ and other greenhouse gases into our atmosphere, that is for sure.

Human influence has been leading to changes in extreme events, and this year we have been experiencing particularly many of such events all around the globe: Wildfires and extreme drought in the Mediterranean, Russia, the USA, and Canada, going along with heat records being broken in these regions and north of the Arctic circle, and heavy rainfall leading to flooding in Central Europe and China, just to name a few from the past weeks.

Climate change needs to be understood and addressed

The need to address climate change - to better understand the physical science behind it, to understand the impacts and how we adapt to it, and to mitigate it - is pressing. Globally, climate policies need to be based on science, and scientists need to provide understandable information for policymakers to support them in focusing on the elephant in the room: climate change, its effects on the planet and us humans, and how to address it. Following the treaty of the United Nations Framework Convention on Climate Change (from 1994), and the Paris Agreement (active since 2016), almost all countries have agreed on battling climate change by reducing greenhouse gas emissions and thus reduce or eliminate our impact on the climate.

IPCC Assessment Reports to inform policymakers

The IPCC - Intergovernmental Panel on Climate Change - was established in 1988 to do exactly that: It regularly provides Assessment Reports for policymakers, based on the most recent knowledge on climate change. The IPCC does not carry out its own research - Hundreds of scientists at the forefront of climate sciences work together to present the newest data and knowledge-based consensus in the field, based on the multitude of publications available, and making it more easily understandable. The process the reports are going through is rigorous, thorough, and robust. The last IPCC Assessment Report was published in 2013/2014, and it is now being superseded by the Sixth Assessment Report, with the first part being made public today. This first part concentrates on the physical science basis. Part 2 and 3 address the impacts, adaptation and vulnerability, and mitigation of climate change, respectively. They will be published next spring. A Synthesis Report, summarizing and combining conclusions from all three parts, will be published afterwards. A short video by the IPCC explains nicely what the Sixth Assessment report is, you can watch it on Vimeo.

Content of the IPCC Sixth Assessment Report

Sebastian Mernild at the IPCC meeting in Guangzhou in 2018. © S. Mernild

Today's report - the summary for policymakers of "The Physical Science Basis" - describes the climate system's physical processes, including climate change as we see it today. It gives the most coherent and up-to-date knowledge on our climate system and man-made climate change. 234 authors worked together on the report, and our former director Sebastian Mernild (now pro-rector and professor in climate change and glaciology at the University of Southern Denmark, and in an adjunct position with NERSC) is a Lead Author on it.

He describes its importance the following way: “This is an interesting report with assessments of the physical climate system and its derived effects. With the latest assessments from the IPCC Sixth Report on our understanding of the observations we make today and our calculations of future trends in the global climate, the importance of human activity for the climate change we already experience today and must expect to occur in the future, is even stronger emphasized than previously. The research on which the report is based therefore provides the necessary evidence to act in relation to the United Nations Framework Convention on Climate Change, as well as the Paris Agreement.”

The quote originates from a debate piece Sebastian Mernild and Jens Hesselbjerg Christensen (co-author on IPCC report) published in the Danish newspaper Berlingske today.

An exciting feature of the new report is the interactive regional climate atlas!

Some of the important conclusions of the report are:

• The current CO₂ concentrations in our atmosphere are as high as they have never been in the past 2 million years at least.
• The current concentrations of other greenhouse gases, such as methane, have not been as high as today for over 800.000 years.
• These greenhouse gas increases since 1750 are much higher than what would be expected due to natural fluctuations – a sound indicator for that human greenhouse gas emissions are the cause.
• The global average temperature increase of 1,09 °C from 1850-1900 to 2011-2020, is almost entirely due to human activity. It is very likely that 1,07 °C are attributed to it.
• Man-made climate change is affecting weather and climate extremes all over the world. An example are heatwaves having become more frequent and more intense in the past decades, and this trend is expected to continue.
• Precipitation patterns have changed globally, and this is also a man-made change. Extreme events are also affected by our emissions of greenhouse gases. Flooding events such like those in Central Europe and China last month are likely to intensify in the near future.
• With increasing global temperatures caused by greenhouse gas emissions, ice caps will continue to melt, and the global sea level will continue to rise. Prognoses assuming no limitations in greenhouse gas output and further increasing temperatures indicate that in one hundred and thirty years from now an increase of up to five meters is possible!

Sixth Assessment Report