"Emissions must come down - right now!"

由 2021年5月18日 发帖 Lucie Maluck

What will happen if we don't limit global warming to 1.5 degrees? Professor Hans-Otto-Pörtner, member of the Intergovernmental Panel on Climate Change, gives a gloomy forecast.

It's been six years since mankind set itself a major goal at the UN Climate Change Conference in Paris: to limit the earth's warming to well below 2 degrees, ideally to 1.5 degrees. As keynote speaker at the at the virtual mtu Marine Summit, Professor Hans-Otto-Pörtner, member of the Intergovernmental Panel on Climate Change and marine biologist at the Alfred Wegener Institute, urges compliance with these targets. "The good news is that we can still achieve the 1.5 degrees," says Pörtner. However, and this is his most important message, this will require rapid and far-reaching changes - in shipping as well as in industry, transport and aviation.

Professor Pörtner, everyone is now talking about the 1.5 degrees of the Paris Agreement. How much leeway do we have before we break this bar?

There is still a margin of just under half a degree to comply with this limit of 1.5 degrees. We have already warmed the earth by 1.1 degrees since we started burning fossil fuels en masse more than 150 years ago with the industrial revolution. But, and this is good and very important news, from a scientific and technical point of view, this target is still achievable.

What do we need to do to achieve this goal?

We need to act quickly and far-reaching: By 2030, we need to reduce greenhouse gas emissions globally by 45% - compared to 2010 levels, and by 2050 we should be at "net zero" - as agreed in the Paris Agreement.

What exactly does "net zero" mean?

It means that no more emissions should be released into the atmosphere. But we won't achieve that, because there will always be emissions that cannot be avoided - from agriculture, for example. But we have to compensate for these by removing CO2 from the atmosphere, so that the net climate balance is zero again. From 2050, we will even need net negative emissions for climate stabilization at 1.5 degrees to compensate for delays in emissions reductions.

In the Intergovernmental Panel on Climate Change, you outlined in a special report the impact that tearing down this target would have. What impact would this have on people?

Already now, with an increase of about one degree, the consequences of climate change are being felt. Sea levels are rising, extreme weather events are becoming more frequent and glaciers are melting in the Arctic. We are already seeing devastating forest fires in Australia and the USA. Heat waves cost many lives every year, not only in Africa, but also in Europe. Each additional increase makes these consequences more dramatic. If warming exceeds 1.5 degrees, the risk of long-lasting or irreversible changes, such as the loss of some ecosystems, or the risk of unstoppable climate change increases.

On 80% of the earth surface climate change affects the life sustaining systems – from the top of t the mountains to the depth of oceans. These changes will continue for generations to come. (Source: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In press.)

What is the impact of climate change on sea level?

Sea level has accelerated in the first decades of this century. If we react now and massively reduce emissions, we can manage to limit the rise to about one meter by 2100. If we do nothing, it will rise by three to five meters by 2300. Then melting ice masses in low-lying coastal and island regions would lead to extreme flooding as early as 2050. Many millions of people would lose their homes.

And what does global warming mean for the oceans?

Climate change alters ocean currents, warming the seas and thus endangering the marine ecosystem. Some of the CO2 from the atmosphere dissolves in the ocean, creating carbonic acid, and the ocean acidifies. There are also heat waves in the ocean, causing further stress to many creatures. Mobile marine life may move to other areas of the ocean. Corals, on the other hand, bleach out. Even if we make the 1.5 degrees, 70 to 90 percent of corals will die. If we go above that, we will lose almost all the reefs. That, in turn, robs fish in nearshore areas of their food base. Low-latitude nearshore fisheries are already at significant risk.

This should be more than a warning to everyone. What can we do to meet the 1.5-degree target?

We must accept the findings of science and base our decisions on them. Everyone can do something, every decision, no matter how small, matters. It makes a difference whether we limit global warming to 1.5 or 2 degrees. We should use all the technologies available to us today and in the future to limit climate change as best we can - and we need to start now, the time for debate is over.

What needs to happen in shipping? Do you see hydrogen as the future?

Hydrogen is an important key to sustainable energy production. It can be used directly as an energy carrier from the hydrolysis of water, or it can be used in the synthesis of fuels by binding and recycling CO2. This would avoid net emissions from shipping and aviation. The problem is that hydrogen synthesis and CO2 bonding are energy-intensive. This could be reduced by selecting appropriate catalysts, but there is still a need for research in this area. In this respect, the path is the goal, we have to push ahead with the energy transition, even if we have not yet answered all the research questions. But that was no different at the beginning of the Industrial Revolution in the 18th and 19th centuries.