How man is changing the balance of the Earth’s climate

By Gary Dagorn

Posted today at 06:57, updated at 08:31

One way to measure how humans are rocking the climate is to observe Earth’s Energy Imbalance (TED), or Earth Energy Imbalance in Newton’s language. The idea here is to focus on how the quantities of energy received and re-emitted by the climate system of planet Earth can be disturbed and go from equilibrium to imbalance.

On very long time scales and in the absence of disturbance, the Earth’s climate strikes a balance between incoming energy (that of the Sun) and outgoing energy (that which is sent back into space). This is called the equilibrium temperature:

  • If an object receives more energy than it loses, its temperature rises
  • As its temperature increases, the object will lose more energy
  • Equilibrium is reached when the energy lost by the object is exactly compensated for by the energy it receives.

Until then, only two forces were able to modify this balance. The first is naturally the Sun, whose activity can increase and decrease, varying the amount of energy that our small planet receives. The second is volcanism. Major eruptions, like that of Mount Pinatubo (Philippines) in 1991, eject tens of millions of tons of particles at very high altitude which, with the winds, cover the entire globe in a few weeks and reflect sunlight. On average, the five largest eruptions of the XXe century have cooled the earth’s climate by 0.25 ° C.

There is now a third force capable of influencing the climate of planet Earth: humans. “Human influence is now strong enough to clearly disrupt the earth’s energy balance”, write the authors of a DET evaluation study conducted by Karina von Schuckmann and her team, and published in Nature in january 2016.

Indeed, the advent of the steam engine and de facto of human industry from the end of the 18th centurye century has come to upset this balance, with a formidable ingredient: greenhouse gases, compounds capable of absorbing infrared rays and retaining heat in the earth system and that human activities will reject more and more as time goes by. and as the years go by and global economic development.

How humans disrupt the energy balance of the Earth

Influence of various factors on the earth’s climate balance since 1750.
The energy flow (called radiative forcing) is expressed in watts per square meter.

Hover to highlight the factors:

human

natural

1750 –
2011

Of course, all the extra energy trapped by the planet’s climate system has to be stored somewhere. But where ? Here are the current estimates:

93% of this energy is absorbed by the oceans especially in shallow water (less than 700 meters from the surface) 4% is absorbed by land and the atmosphere 3% is absorbed by ice cream

In other words, almost all of the solar energy trapped on Earth for 250 years by greenhouse gases emitted by humans has been absorbed by the oceans, which cover 70.3% of the Earth’s surface. A small part only was by land, atmosphere and ice (7%). However, it is this small part that is responsible for almost all of the global warming measured so far (+1 ° C in 2017 compared to the average temperatures of the pre-industrial era).

The tremendous mass of water in the oceans making them extremely slow to heat, themselves slow down global warming, due to their significant inertia. If the Earth had more land mass, global warming would have been much faster – and therefore even more destructive for ecosystems. Thus, even if we reduce our greenhouse gas emissions abruptly, so as to regain a concentration of CO2 Similar to the pre-industrial level, ocean waters would continue to slowly release stored heat.

The threat is all the more real as the rate at which the oceans are absorbing excess energy caused by humans is growing dramatically and has never been higher. These absorbed as much energy between 1997 and 2015 as since 1860, according to a study by Peter Glecker and his team and published in Nature in january 2016. This analytical work, based on several hundred climate models, suggests for the first time that the deepest layers of the ocean, those located at a depth of more than 2,000 meters, beyond the measurement capacities of the beacons. Argo that roam the oceans, also heat up at high speed. “These works show that “Signals” of climate change intensify over time, and more of these “signals “ lie in the depths of the ocean “, according to Dr Matt Palmer, oceanographer at the Hadley Center of the UK Met Office. “The study confirms that the warming of the oceans has continued at the expected rate, “hiatus” is just a surface phenomenon. The Earth is still warming, and the oceans have absorbed most of this heat. “

The oceans have absorbed as much energy in 18 years as since 1860

Percentage change in heat absorbed globally by the oceans between 1860 and 2015. Calculated from comparison of climate models (CMIP5).

  • 0 – 700 m
  • 700 – 2000 m
  • + 2000 m

1860 1880 1900 1920 1940 1960 1980 2000

100% 80% 60% 40% 20% 0

50% in 1997

Due to the ability of the oceans to store this excess energy, which acts as a buffer, average surface temperatures “Are not a good indicator of global warming on these time scales”, concludes Schuckmann. The question of how it is absorbed and by which components is crucial for scientists, because it allows a much better understanding of how the climate will evolve in the decades to come.

The data presented in the first graph come from the simulation of a climate model, called “ModelE2” and created by the Goddard Institute for Space Studies de la NASA (GISS). A climate model is a complex program run on supercomputers to simulate the Earth’s climate and how it will change in the future. The results of this simulation were published by the GISS in 2012 as part of a comparison between climate models (called CMIP5, or Coupled Model Intercomparison Project, Phase five), which was then used to write the fifth assessment report of the IPCC published in 2014. The bands surrounding the curves represent the 95% confidence interval, that is to say that 95% of the simulations made fall within this interval.

The data for the second graph comes from a article published in 2013 in the review Atmospheric Chemistry and Physics. Our work was inspired by that of Bloomberg, published in 2015 (« What’s warming the world? »).

📁 Access the raw data used in this article

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How man is changing the balance of the Earth’s climate

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