A lot has been said and written about humankind generated climate change and whilst most people are very concerned about this, a few are sceptical and/or deny its reality, preferring to think it a conspiracy theory and/or an anti-western / capitalistic anarchistic plot.
As an astronomer I thought it may be helpful to write a straight-forward short article about how global warming is happening. And why the deniers are wrong.
There are 2 major processes which affect global temperature, the amount of heat we receive from the Sun and the amount of heat retained in our atmospheric 'blanket'. I am not an atmospheric chemist and thus cannot write with authority on the latter. But I can for the former, and on how sea ice, the polar ice caps and mountain glaciation are critical for a global temperature equilibrium (balance).
If an object receives more energy than it reflects/radiates, it will get hotter. When we come inside on a cold day we warm up to the temperature of the room. We don't overheat because our bodies become heat-balanced with the room.
Except for gravitational potential and orbital energy (which do not affect global temperature), all the energy received by the Earth's atmosphere is from the Sun (...astronomical friends will allow me to ignore stellar radiation as miniscule in comparison, and geophysical friends please allow me to ignore mantle and core geothermal energy).
The energy received from the Sun into the Earth's atmosphere is called the solar irradiance. This is very stable/consistent. See our blog post of January 2017 for more on this
(Although very small variations are seen in the solar irradiance...short term through the slight eccentricity of the Earth’s orbit and the approximately decadal solar cycle, and long term in orbital changes such as the Milankovitch cycle, these do not account for temperature rises observed.)
Some sunlight is reflected by the Earth's atmosphere, including clouds, and the surface, and not absorbed. It is reflected back into space and does not contribute to the temperature 'budget' of the Earth.
The amount of light an object reflects is call the albedo of the object. The Earth is a relatively shiny planet and reflects about 30 to 35 % of the sunlight incident upon it. The moon is duller, and reflects a more consistent 12% of incident sunlight.
Dark rocks such as charcoal has an albedo of typically 4%, fresh snow is very reflective at circa 90%. Sea water is dull at about 6%, whilst sea ice varies from 50 to 70%. So the duller an object, the more heat it absorbs.
The problem we have is that the reduction in area (by melting) of the ice caps, sea ice and mountain region glaciation is reducing the global albedo. This means that our planet is no longer in thermal equilibrium (heat balance) and our atmosphere is heating up.
It’s analogous to us living in a greenhouse. We have reflective foil on our roof which means our greenhouse doesn't heat up too much. But what is happening is our reflective foil (ice) is being removed. So we're heating up. And life in our greenhouse will change.
This is why ice is so important to us. And why we need to be both very worried AND active in every which way we can to ensure we do not compromise our icy regions.
The second major process governing global warming is retention of heat. Retaining heat is rather sensitive to atmospheric chemistry, with water vapour, carbon dioxide and heavier 'greenhouse' gases such as methane all adding to heat retention. We will each have heard lots on these latter processes. In our greenhouse analogy, not only have we ripped down our reflective foil, but we've decided to put a warm coat on too!
There is very much more to this topic and many atmospheric aspects than this short article can provide. But albedo, and thus ice is absolutely critical.
I've included a few links below from the popular media for further info. as to the issues we're facing, and a link to my ideas as to what we each individually can do.
The last 3 of these links show, in my opinion, how the current US administration (who you will probably know has withdrawn from climate change commitments and accords) should be considered as a global terrorist, aided and abetted by the UK Johnson administration.
Strong words I know, but please read this and the links below and you'll understand why I use such rhetoric.
The rate of loss of ice in Greenland
Himalayan glaciation loss
The accelerating rate of loss of Artic permafrost
How the US administration are actively supporting reduction in Artic ice.
How the UK government response is a sham
How little importance the UK PM Johnson considers this matter to be
But what can I do to help? Plenty!