All the risks of climate change

The “worst case scenario” outlined by Professor Giorgi predicts an increase in the Earth’s average temperature of two degrees by 2050 and four degrees by 2100 due to global warming caused by emissions of greenhouse gases such as carbon dioxide (CO2) and methane (CH4).

Professor Giorgi, you have posited that if the recent Paris Agreements concerning climate change are not implemented, the average temperature of the Earth could rise by more or less two degrees by 2050. Is this a realistic scenario and what would be the consequences?
There are diverse phenomena associated with a rise in global temperatures. On one hand, there will be further melting of the arctic ice caps in addition to what has already taken place. The same phenomenon will occur with the ice in Greenland and the Western Antarctic as well as the five continents’ major glaciers, which are also receding. And this is one of the main problems: the ice serves as a fundamental reserve of water for mankind, a reduction in the ice means a reduction in available fresh water.

The second phenomenon is the rising sea levels, which is caused exactly by the melting of the continental ice and, to a lesser extent, by the thermic expansion of water. The arctic ice does not influence this because if an iceberg melts, the sea level remains the same: this is Archimedes’ principle. In order to explain this, if an ice cube in a glass melts, the level of liquid in the glass remains the same, while if we were to melt the ice cube in the palm of our hands and then pour the melted water into the glass, we would have a larger quantity of water and thereby a higher level.

That said, let’s return to 2050. Based on the worst possible scenario, we will have an average rise in sea levels of around 30cm; they have already risen by 20cm in the last century. We can imagine consequences such as a greater risk of coastal flooding, the erosion of the coasts and the intrusion of salt water into the soil, which is happening already in the Nile Delta, and this would damage the fertility of the land. In Bangladesh, a country whose coastal area is located largely below sea level, the monsoons could bring floods that are even more devastating than today’s. Coastal populations are facing a clear threat and we should remember that a large proportion of the Earth’s inhabitants live near coastlines and their number is increasing.

Then there’s a third phenomenon: the intensification of the hydrological cycle. The warmer the air becomes, the more water vapour it will contain. Therefore rains will become more intense, a phenomenon that since the 1970s has become quite evident. At the same time, temperature rises can mean that it rains less frequently, because the warmer the air, the longer it takes to reach saturation point, especially if the land is drier. In other words there will be longer dry periods and more intense rainy periods.

How can we become fully aware of what climate change really means?
Approximately eighteen thousand years ago the last ice age reached its peak. Average temperatures were around 4-6 degrees lower than now. In other words, the temperature difference between an ice age and an interglacial period is more or less the same as the difference between current temperatures and those forecast for 2100 in the worst-case scenario. However the passage from a pre ice age period to the ice age occurred naturally over thousands of years. We in the industrial age would experience a similar change in temperature in just one hundred years!

Now if we look at the fact that human society in the last ten thousand years has developed because the climate has been very stable, it is impossible to ignore how a similar change, in just one hundred years, would be something so enormous that it could potentially completely disrupt the climate, vegetation and the oceans in ways that are as yet difficult to ascertain because the Earth system is not linear. In other words, in the worst-case scenario, our grandchildren and their children would live in an environment that is very different from its current state.

Can the Paris Agreements avoid environmental catastrophe?
The agreement aims to limit global warming to the extent that temperatures do not rise to more than two degrees above preindustrial levels, therefore, by around one degree compared with current levels given that global temperatures have risen by around one degree since the beginning of the 20^th century. In order to achieve this, it is necessary that the quantity of CO2 in the atmosphere, the increase of which is the main factor that contributes to the global warming taking place, is stabilized at a level of more or less 450 - 500 parts per million, not far from the current value of around 400 parts per million (in the scenario known as RCP 8.5, the quantity of CO2 could reach 950 parts per million by 2100). But to stabilize these values it is necessary to reduce emissions of gases that cause the greenhouse effect, such as CO2. This can be done through a reduction in the use of fossil fuels, the main cause of CO2 emissions resulting from human activity.

How can this be done?
The first intervention concerns energy efficiency. The second crucial passage concerns renewables. I have to say that there has been notable progress in this field, so much so that I personally consider the age of oil to be at an end. Significant momentum is coming from emerging countries like India and China, which today are among the main producers of CO2. Their governments have understood that pollution, above all in the large cities, has become unsustainable. Therefore, they have made significant efforts to shift towards renewable energy. China is at the forefront of photovoltaic energy and electric cars, and the ambition is to play a leadership role worldwide. In India recently they have launched the “solar mission” that entails the installation of photovoltaic panels in all Indian homes by 2030.

How much impact will climate change have on the economy?
Every sector has different characteristics but in each field it is now unthinkable not to consider climate change when drawing up a long-term strategy. Insurance companies, for instance, are developing policies that contemplate the potential for catastrophic events. Different governments are rolling out policies to adapt to this. An example is the coastal barriers in Holland, which are being built up. The same is happening with the banks of the Thames to cite another example. These are opportune measures because from this point until if and when the situation becomes stabilized, global warming will continue to produce negative effects.