The relationship between space debris and climate change

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The UK will host the 26th UN Climate Change Conference of the Parties (COP26) in Glasgow from 1 – 12 November 2021, but there’s nothing on the website ( to suggest that space debris is on the agenda…but perhaps it should be.

This may seem a surprising statement since the existential risks from rising sea levels and increasing atmospheric carbon dioxide are far more of a direct threat to human activities than space debris.

A more considered view, however, demonstrates how important it actually is to extend the principle of “caring for the planet” to include also “caring for the near-Earth environment”.

Why? Well, just as runaway greenhouse gas emissions are considered to be a threat to our existence on the planet, so an exponential growth in the debris population in Earth orbit, known as the Kessler Syndrome, could be a threat to our continued utilisation of space.

If you’re yet to be convinced that this would be a problem consider just how dependent we are on satellites for information relating to climate change and our anthropogenic effects on the planet. Half of the 50 Essential Climate Variables monitored by the Global Climate Observing System are tracked from space.

The “ozone hole” over Antarctica, one of the first high profile demonstrations of mankind’s, (or should that be man-unkind’s?) ability to harm the atmosphere, has been monitored using satellites for more than 35 years. Many other greenhouse gases can now be measured from space, and any international carbon trading system in the future would almost certainly have to be based on satellite data.

Satellites are used to measure sea temperatures too, tracking the way in which heat is redistributed around the planet by ocean currents. Air temperatures around the planet are also monitored from orbit. Microwave instruments on polar-orbiting missions measure the energy emitted by oxygen molecules in the troposphere.

The effects of this additional energy in the atmosphere are measured from space; on short timescales by weather satellites, which can monitor the frequency of major storms; and on longer timescales by science missions such as Grace, which can detect the subtle variations in gravity that result from ice caps melting in Greenland, Antarctica, and elsewhere. The measurements made by these satellites are so subtle that they can detect both seasonal and longer-term changes in the water table around the planet too.

Climate models obviously rely to a significant extent on cloud data collected by satellites, but also on crucial parameters such as total solar irradiance (TIR). The Earth is not a closed system, and the radiation from the Sun varies on an 11-year cycle. At the peak of the cycle, more of the Sun’s energy is emitted in the UV and X-ray regions of the electromagnetic spectrum, and since the Earth’s atmosphere preferentially absorbs these wavelengths, the solar input to the Earth’s energy budget changes periodically too. And how do we measure TIR? Yup, you guessed it – from orbit.

To conclude: the good news is that a piece of space debris is very, very, very unlikely to land on your head any time soon. But unless we include the sustainability of the space environment in a holistic approach to cleaning up the planet, our ability to use satellites to monitor the climatological changes that we care about could be significantly compromised. And that would be bad for everybody.

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