We live on a planet that has become small for us, how small the room from our childhood games seems when we return to it as adults. The earth’s circumference is just over 40,000 km in length, a distance that we have accumulated many times over on the odometers of our cars.

On this “small” planet we already live more than 8 billion inhabitants every day, consuming an enormous amount of resources and producing an immense volume of waste. It does not seem daring to think that we will be causing some effect on Earth on a global scale. Science confirms it, being the first and most visible manifestation of this human condition on the planet the so-called global warming.

Global warming and its effects

Throughout the 1980s, the global average surface air temperature began to increase, although such a rise could still be explained by the highly irregular natural behavior of climatic variables.

Entering the last decade of the last century, the clear thermal increase verified in the series of records of innumerable meteorological stations from the observations of artificial satellites and in natural indicators began to be statistically significant. One could already speak of global warming.

The Sixth Report of the IPCC, which constitutes the most complete evaluation of the recent evolution of the climate and its future projection, has established the increase in temperature in the second decade of the 21st century at 1.1 ℃ with respect to the reference period established in the second half of the 19th century.

A temperature rise of one and a tenth degree in more than a century does not seem like much. But such a value in a little over a hundred years is a very important increase at a global level, which represents a huge storage of heat in the Earth system.

The thermal increase today would be 1.2 ℃, close to the degree and a half that is considered a threshold that should not be reached, as has been repeatedly recalled and agreed at international COP meetings (conference of the parties). Otherwise, very serious or irreversible effects would be derived for life and our property.

Warming brings other effects, such as shrinking Arctic sea ice and Greenland and Antarctic land ice, and the near-widespread retreat of mountain glaciers.

Another disturbing effect is the rise in sea level, which is estimated on average at about 4 mm per year. It is difficult, as is the case with the increase in temperature, to convey concern to the general public about a fact that may be seen as insignificant, but which in a century would mean a two-span rise in sea level, with the consequent negative impact on the coasts, often densely populated.

The vulnerability of the Mediterranean basin

In the area of ​​the Mediterranean basin, where a large part of mainland Spain and the Balearic Islands fall, the increase in temperature has been higher than the global one, and one can speak of a hot spot, that is, a region particularly sensitive to warming. A recent estimate placed it at 1.4℃, which today would already reach a degree and a half.

Rainfall, contrary to temperature, still does not present trends in most of the regions, although the seasonal rainfall regime has changed in many cases with the decline in spring precipitation, vital for rainfed crops, in favor of the autumnal

Droughts and heat waves

The increase in meteorological risks is another feature of climate change: they are already more frequent, intense and long-lasting. In the case of Spain, they mainly take the form of heat waves and droughts.

When both phenomena appear at the same time, as in the summer of 2022, with drought in many Spanish communities together with heat waves in each of the summer months, their effects on agriculture, ecosystems and, in general, on the economy are more serious than the sum of those produced by both extremes separately.

The tropical nights and the torrid nights

In the cities of the southern half of Spain and the rest of the Mediterranean coast, the local phenomenon of the heat island -warming up in the center of cities in contrast to the periphery at night- is giving rise to a very striking increase in tropical nights. Defined as those in which the thermometer does not drop below 20 ℃, they are nights of bad sleep.

The appearance or greater frequency of nights with a minimum temperature equal to or greater than 25 ℃ has even been observed, for which we have proposed the name of hot nights.

Excess heat has a negative impact on the health of the elderly or those with chronic diseases, increasing their morbidity and mortality. This circumstance is particularly critical in the case of people who live in a situation of energy poverty, that is, who do not have an air conditioning unit or cannot use it due to the high cost of energy.

Fossil fuels and the climate emergency

If the evidence of global warming is so explicit that it is no longer discussed in denialist circles, its cause –the latest workhorse for denialism– is today unequivocal for science: the emission of greenhouse gases caused mainly by the burning of fossil fuels (coal, oil and natural gas) and the general changes in land use. There is no need, then, to waste time in futile debates.

If we return to the global perspective, today there is talk of a climate emergency. This has been declared or adhered to by public institutions, universities and research centers and other entities and groups.

The climate system, particularly the ocean, presents a great inertia in its thermal behavior. Marine waters do not change temperature easily.

Water is a substance that has a high specific heat, so a lot of heat must be supplied to it to raise its temperature and it must also lose a lot of heat to lower it. This means that, even if the use of fossil fuels were prohibited tomorrow, it would take a few decades until warming was reversed.

Hence, it is necessary to act with the utmost urgency so that it is the minimum possible. To make an analogy, the planet is like an ocean liner that, when approaching the port, is traveling at a higher speed than it should be or on the wrong course. At the last minute we will not be able to avoid colliding with the pier due to the inertia of its movement.

climate future

Climate models tell us that with a major effort to reduce greenhouse gases in the remainder of the decade, specifically, a 45% reduction compared to 2010 emissions, we would be able to achieve so-called carbon neutrality by mid-century . In other words, in 2050 the emissions that could be produced would be balanced with the captures by natural systems or through certain technologies.

In this way, it would reach 1.5 ℃ of warming, to drop slightly and be below that threshold by the end of the century. In the event that we continue to base our energy model on fossil fuels and, in general, with a consumerist economic model with GDP as the main indicator of progress, the temperature would shoot up to more than 4 ℃ of warming by the end of the century, a unimaginable scenario.

The future depends on us, on the 8 billion humans, which will be close to 10 billion by the middle of the century. In any case, in addition to the mandatory mitigation, that is, the reduction of greenhouse gas emissions, adaptation to the new climatic conditions is also required to reduce the risks they entail.

This article was originally published in Fundación Telefónica’s Telos magazine.

Javier Martín Vide, Professor of Physical Geography, Barcelona University

This article was originally published on The Conversation. Read the original.