One thing most people don’t get about climate change
I first came across climate change at university in the late 1990’s, doing basic calculations of energy transfers across multiple levels in the atmosphere. Even at that basic level, how increasing greenhouse gas levels in the atmosphere can trap more heat in the Earth’s climate system became very clear, at the same time that it also became apparent just how complicated the Earth’s climate and climate change is. There are an awful lot of processes happening around the world, interacting with each other all of the time on all sorts of scales.
It is increasingly hard to ignore now that something is going on:
Global temperature since 1850
Most people now acknowledge the climate is changing…the overwhelming majority. But there are still a number who argue, or at least are not sure if, the changes are from some sort of natural cycle.
Yes there are other things that impact the Earth’s climate besides greenhouse gases. Large volcanic events can lead to significant cooling for a year or two from the particles they cause that reflect away more of the Sun’s energy, before the particles fall out of the atmosphere. The variability in the sun spot cycle does cause some variability in the amount of energy coming from the Sun. Milankovitch cycles in the tilt of the Earth’s axis and how circular the Earth’s orbit is cause cycles over ~25,000 to 100,000 year time frames that trigger changes that can send the Earth into and and out of ice ages, or into warmer periods like we have seen for the last ~20,000 years. And there is still significant variability in the Earth’s climate system year to year from variability such as El Nino and La Nina events.
The problem with the above influences is that none of them explain the strong warming over the last 100 years or so, in particular since the 1960’s. From astronomers, the Milankovitch cycle is currently in a neutral state, and operates much too slowly to explain what is happening over a 50 to 100 year time frame. The Earth is at least 150,000 years away from the next ice age. Activity from the Sun has decreased since the 1990’s, while temperatures have climbed.
Back at university in the 1990’s greenhouse gas levels were up at about 360 parts per million from the roughly 280 part per million they were prior to industrialisation commencing in the 1800’s. I saw them hit 400 ppm in 2013, and they are now at ~415ppm. The basic theory underneath climate change is that increasing levels of carbon dioxide and methane and other greenhouse gases will increasingly stop more heat energy escaping to space out of the top of the atmosphere, sending it back to the surface of the Earth. Calculations similar to those I did at university show that this should happen, and repeated comprehensive computer modelling backs this up.
Science is about being curious, asking good questions, and looking for evidence that might support or challenge a question or theory. For the idea that increasing greenhouse gases will change the energy balance in the atmosphere, a great scientific question to ask is “Do we see direct evidence of changes in the energy balance in the atmosphere”.
The simple answer is yes. Yes we do see that. Comparing satellite measurements over recent decades of the amount of heat energy going to space shows there is less heat going to space in the particular wavelengths that greenhouse gases have influence on:
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.131.3867
Also, separate observations at the surface show increasing heat coming back to the Earth’s surface:
https://ams.confex.com/ams/Annual2006/techprogram/paper_100737.htm
And as well as warming on land- with the ocean covering 70% of the Earth surface- measurements of ocean heat content show increasing amounts of the extra heat going into the oceans:
https://www.atmos-chem-phys.net/11/13421/2011/acp-11-13421-2011.pdf
As one of the papers states, all of this is the last nail in the coffin for the idea that what we have been seeing over the last few decades is a natural cycle.
Human emissions and the resulting increasing greenhouse gas levels in the atmosphere are driving the warming around the planet in recent decades.
End of story.
So why does this matter? Climate change is already impacting us significantly just from the ~1 degree C warming that has already happened, and some further climate change is unavoidable from the lags in the climate system.
But, very importantly, what we do or don’t do over the next 20 years will impact the planet for many thousands of years, particularly around the amount of sea level rise that occurs.
We can act strongly over the next 20 years in reducing emissions - and it will require a concerted, perhaps emergency effort- and minimise the amount of change. Or we could continue to drag our feet, and lock in very large amounts of further change that impacts many generations to come, and make our inter-connected, complex human civilisation difficult to maintain for the more than 7 billion of us on the planet.
Reducing emissions is really a planet wide harm minimisation exercise- particularly after our wasting the last 20 years. Climate change will not kill us all- but will have huge impacts we have the opportunity to very significantly minimise.
Look at what you can do to reduce your own emissions. Fly less, drive less, eat less meat, use less electricity, but most importantly, get active and hold our policy makers to account for their failure to respond as they should be to this issue. Current policies around the world are about one third of what is needed to meet the 2 degree C Paris Agreement target. So we need to double or actually triple down policies and action, and get stuck in now.
Electricity emissions are coming down from renewables, but that is only part of the answer. A comprehensive suite of research, plans and policies is needed to address emissions from all areas of human activity. The lack of action, plans and policies is why more and more people are taking to the streets in movements like 350.org and Extinction Rebellion https://rebellion.earth/.
So please share this. When you come across someone who says its just a natural cycle let them know that is not, and there are direct observations that show that. And ask them what kind of planet do they want to leave for their children and grandchildren.
We cannot afford to squander the remaining window of opportunity we have to minimise the harm to us and the planet.
