Why Should We Limit The World’s Temperature Increase to 1.5C?

The IPCC say that we need to limit the global temperature increase to 1.5C rather than 2C or even 3C. This is measured from global temperature before the first industrial revolution of about 1760. I can’t tell a 0.5C difference in temperature, but it seems that the world can tell every change smaller than this. Having learnt a little more of the science, and reading more news, I kept seeing a reference to a global average temperature increase of 1.5C. I didn’t know what this was referring to, but it turns out to be a very important report written in 2018.

How Does the World Work?

The world’s climate is determined by air temperature, ocean temperature, and how air and water moves about the planet, which is determined by water temperature and air pressure. Everything in the Earths systems are linked. Our climate is like a finely tuned Swiss watch with a huge amount of moving parts. Change one part, and everything else has to adjust. In doing so, the time on the watch changes. It will tell a different time.

The world also has feedback loops, so as changes happen, they can make other changes. These can intensify on each other, and the changes intensify. If one domino is knocked down, then it can case many others next to it to also fall. You can see how in non scientific terms it is possible for the watch hands to start spinning faster and faster, or for climate change to accelerate in pace.

What Is Currently Happening?

This section is devoted to the seminal report produced by the IPCC in October 2018. To set the scene, below is a summary taken from the European Environment Agency The European environment — state and outlook 2020, read more here.

The environmental and sustainability challenges that we all face today are rooted in global developments stretching back over decades. During this period, the ‘Great Acceleration’ of social and economic activity has transformed humanity’s relationship with the environment. Since 1950, the global population has tripled to 7.5 billion; the number of people living in cities has quadrupled to more than 4 billion; economic output has expanded 12-fold, matched by a similar increase in the use of nitrogen, phosphate and potassium fertilisers; and primary energy use has increased five-fold. Looking ahead, these global developments look set to continue increasing pressures on the environment. The world’s population is projected to grow by almost one third to 10 billion by 2050. Globally, resource use could double by 2060, with water demand increasing 55 % by 2050 and energy demand growing 30 % by 2040. (This is quite a summary).

The Earth is experiencing exceptionally rapid loss of biodiversity, and more species are threatened with extinction now than at any point in human history. Indeed, there is evidence that a sixth mass extinction of biodiversity is under way.

The IPCC say we should be living Within Our Means

Our collective goal should be that we should live within the means by which Earth can provide us with. We should live within the planet’s ecological limits. Our prosperity and healthy environment should stem from an innovative, circular economy where nothing is wasted and where natural resources are managed sustainably, and biodiversity is protected, valued and restored in ways that enhance our society′s resilience. Our growth should be low-carbon and should be decoupled from resource use, setting the pace for a safe and sustainable global society.

The United Nations (UN) Sustainable Development Goals detail how this change can happen with social, economic and environmental goals, see them all here. The impacts of climate change on biodiversity and ecosystems are expected to intensify, while activities such as agriculture, fisheries, transport, industry and energy production continue to cause biodiversity loss, resource extraction and harmful emissions. Europe and us all have to look at each of these to see how it can do better.

Europe and other nations cannot simply grow economically and reduce pollution and then think that all will be fine.

The global response to the Covid-19 pandemic could be seen as a rehearsal of what is needed in the future. In 2020, Europe and the world have a unique window of opportunity to respond to sustainability challenges. Now is the time to act.

The central objective of the Paris Agreement signed in April 2016 by 195 Countries had as its long-term temperature goal to hold global average temperature increase to “well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels”.

Why Should We Limit The Global Temperature Increase to 1.5C?

The answer is this:

If we don’t then life on Earth will be much harder for billions of people because of drought, floods, heatwaves and fires. If we can limit the increase to 1.5C then we have a chance of being able to cope with this. If we don’t it gets a lot worse. We already have severe consequences from an increase of 1.1C.

In one of its most ground-breaking reports, Special Report: Global Warming of 1.5ºC, which was released in October 2018 tells us why we have until 2030 to achieve this goal.

Why Do We Have Until 2030?

The answer is this:

Air temperature is determined by how much CO2 and other gases are in it, just like a room temperature is determined by how many radiators are in it. Put lots of gas in the air and it heats it up. We have worked out that there is a limit to how much gas we can put in the air. After this point then we have worked out that the air temperature will rapidly rise. Its a bit like trying to keep the lid of a pan of boiling water. At current rates of gas emissions - which are increasing, then by 2030 we will have put too much gas in the air. The lid will have blown off the saucepan by 2031.

The summary below is taken from The Guardian newspaper on 8th October 2018. Its thorough journalism in the same way that the report is thorough science. Read the full article here.

The world’s leading climate scientists have warned that there are only a dozen years for global warming to be kept to a maximum of 1.5C, beyond which even half a degree will significantly worsen the risks of drought, floods, extreme heat and poverty for hundreds of millions of people.

The authors of this landmark report by the UN Intergovernmental Panel on Climate Change (IPCC) say that urgent and unprecedented changes are needed to reach the target, which they say is affordable and feasible although it lies at the most ambitious end of the Paris Agreement pledge to keep temperatures between 1.5C and 2C.

The half-degree difference could also prevent corals from being completely eradicated and ease pressure on the melting of ice in the poles.

“It’s a line in the sand and what it says to our species is that this is the moment and we must act now,” said Debra Roberts, a co-chair of the working group on impacts. “This is the largest clarion bell from the science community and I hope it mobilises people and dents the mood of complacency.”

Policymakers commissioned the report at the Paris climate talks in 2016, but since then the gap between science and politics has widened. 

Following devastating hurricanes in the US, record droughts in Cape Town and forest fires in the Arctic, the IPCC made it clear that climate change is already happening, upgraded its risk warning from previous reports, and warned that every fraction of additional warming would worsen the impact.

Scientists who reviewed the 6,000 works referenced in the report, said the change caused by just half a degree came as a revelation. “We can see there is a difference and it’s substantial,” Roberts said.

What Happens If Temperatures Increase to 2C?

At 1.5C the proportion of the global population exposed to water stress could be 50% lower than at 2C, it notes. Food scarcity would be less of a problem and hundreds of millions fewer people, particularly in poor countries, would be at risk of climate-related poverty. At 2C extremely hot days, such as those experienced in the northern hemisphere this summer, would become more severe and common, increasing heat-related deaths and causing more forest fires.

But the greatest difference would be to nature. Insects, which are vital for pollination of crops, and plants are almost twice as likely to lose half their habitat at 2C compared with 1.5C. Coral would be 99% lost at the higher of the two temperatures, but more than 10% have a chance of surviving if the lower target is reached.

Sea-level rise would affect 10 million more people by 2100 if the half-degree extra warming brought a forecast 10cm additional pressure on coastlines. The number affected would increase substantially in the following centuries due to locked-in ice melt.

Oceans are already suffering from elevated acidity and lower levels of oxygen as a result of climate change. One model shows marine fisheries would lose 3 million tonnes at 2C, twice the decline at 1.5C.

Ice-free summers in the Arctic sea, which is warming two to three times faster than the world average, would come once every 100 years at 1.5C, but every 10 years with half a degree more of global warming.

Time and carbon budgets are running out. By the middle of this century, a shift to the lower goal would require a supercharged roll-back of emissions sources that have built up over the past 250 years.

The IPCC maps out four pathways to achieve 1.5C, with different combinations of land use and technological change. Reforestation is essential to all of them as are shifts to electric transport systems and greater adoption of carbon capture technology.

“We have presented governments with pretty hard choices. We have pointed out the enormous benefits of keeping to 1.5C, and also the unprecedented shift in energy systems and transport that would be needed to achieve that,” said Jim Skea, a co-chair of the working group on mitigation. “We show it can be done within laws of physics and chemistry. Then the final tick box is political will. We cannot answer that. Only our audience can – and that is the governments that receive it.”

Bob Ward, of the Grantham Research Institute on Climate Change, said the final document was “incredibly conservative” because it did not mention the likely rise in climate-driven refugees or the danger of tipping points that could push the world on to an irreversible path of extreme warming.

The report will be presented to governments at the UN climate conference in Poland at the end of this year. But analysts say there is much work to be done, with even pro-Paris deal nations involved in fossil fuel extraction that runs against the spirit of their commitments. Britain was pushing ahead with gas fracking, although this was halted in August 2019, Norway with oil exploration and the German government wanted to tear down the  Hambach forest to dig for coal. although this has now been protected.

The authors of the report are refusing to accept defeat, believing the increasingly visible damage caused by climate change will shift opinion their way.

“I hope this can change the world,” said Jiang Kejun of China’s semi-governmental Energy Research Institute, who is one of the authors. “Two years ago, even I didn’t believe 1.5C was possible but when I look at the options I have confidence it can be done. I want to use this report to do something big in China.”

James Hansen, the former NASA scientist who helped raised the alarm about climate change, said both 1.5C and 2C would take humanity into uncharted and dangerous territory because they were both well above the Holocene-era range in which human civilisation developed. But he said there was a huge difference between the two: “1.5C gives young people and the next generation a fighting chance of getting back to the Holocene or close to it. That is probably necessary if we want to keep shorelines where they are and preserve our coastal cities.”