The forecast: a hot mistake to our detriment

This week the annual climate conference convenes in Madrid and it seems that even the pessimistic forecast of the Paris Agreement is much lower than expected in reality. According to two new models by climate researchers, the average global temperature towards the end of the century will be significantly higher than expected

Ran Ben Michael, Angle, Science and Environment News Agency

The challenge facing Israel and the countries of the world is becoming more and more difficult: for example, the global average temperature of the surface of the sea and the land last September was the hottest since measurements began in 1880 (equal to the record temperature measured in 2015). In fact, to feel the effects of climate change it is enough to go outside: last week the average temperature in Israel was four degrees higher than the historical multi-year average.

Yes, the climate crisis is already here and the change it will bring is inevitable. But what is the degree of change? How much will the global average temperature rise, what will be the difference between the temperature of the sea and that on land, what will be the difference between different places, and what about the concrete consequences of these differences?

Researchers from different fields of knowledge are trying to answer these and similar questions using models, computer simulations of the rate of change that will occur in the global climate. Beyond the varied knowledge required of the researchers, these simulations require the collection of big data (big data) about the climate in the past, present and near future and enormous computing capabilities. Therefore, this research effort is based on international collaboration between many research centers. Now, a new forecast by a group of scientists from about 30 institutions in France, based on two models, predicts that the temperature increase will be significantly higher than expected so far.

What world do you live in?

Climate models are not a theoretical exercise and are an important element in the process of dealing with the crisis. Assessment reports of the Intergovernmental Panel on Climate Change (IPPC) are published every few years and are based on the latest models; The fifth and last report was published in 2014, and the new model from France is the first published by the research community for the next round that will begin in 2021.

These reports process the entirety of scientific knowledge about the climate crisis and translate it into practical recommendations for policy measures. The 2014 report, which relied in part on models from 2012, is the knowledge base of the international agreement for the mitigation of the crisis (Paris Agreement) and for the preparedness plans of the various countries.

To place the results of the models in a certain context, scenarios were built about the future image of human development. One set of scenarios (called 'Representative Carbon Dioxide Concentration Pathways', RCP - Representative Concentration Pathway) is based on an assessment of the timing of the peak of greenhouse gas emissions during the 21st century and the degree of maintenance of actual emission reductions until the end. Four of the scenarios (RCP 2.6, 4.5, 6.0, 8.5) cover the range between the optimistic - peak emissions will occur in the current decade and continue to decline in the future - and the pessimistic, according to which there will be no reduction in emissions at all. By the way, the number in the scenario is not a degree of change in the average temperature in degrees Celsius, but a measure of the amount of heat from the sun's energy that will be left on Earth as a result of the concentration of greenhouse gases in the atmosphere.

These scenarios were based on physical variables only. At the same time, scenarios were also developed that include additional variables (called "Shared Socioeconomic Pathways" SSP). These are more complex scenarios because variables such as population size, economic growth, or technological development will generate a degree of international cooperation and different capacities in dealing with the crisis. This complexity has led to these scenarios reaching maturity and usefulness only today. The narratives are optimistic or pessimistic depending on the degree of challenge they pose to adaptation or domestication: a sustainable and egalitarian world (SSP1) is less challenging than a world of nationalism and regional rivalry (SSP3) or of intensive and energy-intensive economic activity (SSP5). When adjusting each scenario to the extent of its emissions, the average temperature at the end of the century can be estimated; Even in the rosiest scenario, the temperature will rise by at least 3 degrees (without warming and adaptation measures).

We still do not live in a sustainable and egalitarian world and today it is clear that the optimistic scenario (RCP2.6) will no longer materialize. The World Climate Report 2015-2019, published by the World Meteorological Organization ahead of the UN Climate Conference in September, clearly states that the rate of greenhouse gas emissions and their concentration in the atmosphere continue to increase and the changes they bring (such as heat waves) and the rate of these changes (the increase in the average temperature in the sea And on land, rising sea levels, disappearing glaciers, acidifying the oceans and more) are happening more frequent or severe.

The forecast of the new models from France makes the pessimistic scenarios even more gloomy. In the combination of the worst scenarios of all - accelerated economic development without a reduction in emissions - the average temperature will rise on average by up to 7 degrees; According to all analyzes in such a situation the life-supporting ecosystems will no longer perform their function. This estimate is more than 2 degrees higher than the pessimistic scenario before the Paris Agreement, which predicted an increase of about 5 degrees on average "only", in which it will also be difficult for the human race to survive with reasonable well-being.

The most optimistic scenario according to the new models is an increase of 2 degrees on average by the end of the century - the top goal of the Paris Agreement - and it can only be realized with the achievement of net zero emissions as early as 2060 with a high level of international cooperation in sustainable development. In order to meet the ambitious goal of the Paris Agreement - an increase of up to 1.5 degrees - mitigation and adaptation efforts should be aimed at a more aggressive carbon concentration scenario (RCP1.9), when the current scope of efforts is far from bringing about this situation.

right on the spot

Models linking greenhouse gas emissions to global warming have been developed since the 1970s and are consistent in their findings, including a successful prediction of an increase of about half a degree by the end of the 20th century. However, one of the shortcomings of the models so far is the lack of accuracy on a local scale; This is also the main criticism of their applicability. The work on the model by the French team, which included about 100 researchers, also managed to focus on the country level, in this case France itself and its overseas territories. The models predict extreme events such as consistent heat waves, violent rain showers, tropical storms or a drastic reduction in precipitation in the Mediterranean basin.

The ability to reach these predictions was achieved thanks to the progress in the resolution of the information and the quantities of variables from many fields that were processed during 500 million hours of two supercomputers that processed 20 petabytes (20 million gigabytes). On the other hand, the size of the research community, the level of sophistication of the models, the complexity of the scenarios, advances in computing capabilities and the amount of reports have not changed the bottom line that has been known for at least the last 50 years: continued emissions of greenhouse gases into the atmosphere will intensify the climate crisis. The lack of a quick response by humanity that would include a dramatic reduction in the scope of emissions of the various greenhouse gases and extensive preparation for climate change could endanger the continued existence of human civilization as we know it.

Prof. Yoav Yair, expert in earth sciences and dean of the School of Sustainability at the Interdisciplinary School in Herzliya, explains that "the differences between the various models, despite different results, are not large and stem from the emphasis given to climate variables and the algorithms they use. But all the models, and the reports based on their results , describe a consistent and orderly narrative of the worsening climate crisis. Additionally, neither model predicts cooling, even in scenarios of reducing emissions from now on. The scientific community has to a large extent provided the information and its consequences as well as the desired steps to be taken; now the political arrangement and the economic motivation must be found to strengthen an enforceable mechanism to deal with the crisis."