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The Climate Change Challenge

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The next post in our Climate Conversations series is an overview of the causes and challenges of climate change by Dr Martin Meadows. Dr Meadows is a scientist who is based in Sussex and has worked in research and policy on environmental topics, including climate change, since 1984. He was invited to the Booth Museum to talk for our Climate Change event season, which is currently postponed.

What is climate change?

The science of climate change has been around for well over a century – it’s basic physics and chemistry.[1]

Photo by Dennis SchroederNREL. CC BY-NC 2.0

Photo by Dennis SchroederNREL. CC BY-NC 2.0

Our atmosphere surrounds the earth like a blanket, keeping us warm. The Earth’s atmosphere contains greenhouse gases: these are gases that trap heat.[2] 

When energy from the sun reaches the surface of the Earth, it tries to radiate away but most of it gets blocked by these greenhouse gases. Without greenhouse gases in the atmosphere, the Earth would be tens of degrees cooler.[2]

The most important greenhouse gas is carbon dioxide (CO2).[3,4] CO2 remains in the atmosphere for a long time and changes in atmospheric CO2 concentrations persist for thousands of years.[5] There are other less significant greenhouse gases such as methane and nitrous oxide.[3,4] 

If we add more greenhouse gases to the atmosphere, it will warm up.[2] 

By burning fossil fuels for energy, we have been pumping CO2 into the atmosphere at an unprecedented rate for the past 200 years.[6] CO2 from fossil fuels accumulates in the atmosphere and makes the earth warmer.[3] 

Why is stopping the burning of fossil fuels so important?

There’s global political agreement that humanity’s well-being and prosperity requires the world to keep average global warming well below 2°C.[7]  

The world at best is currently on course for at least 3°C of warming.[8] That level of warming would be a disaster.[9]

What must change to remain well below 2°C?  

Global temperatures are linked to how much CO2 there is in the atmosphere.[10]

To stay well below 2°C, there is a finite amount of CO2 that can accumulate in the atmosphere. This amount is the ‘carbon budget’. 

At the current rate of emissions (at the time of writing, May 2020), the carbon budget that gives a good chance (a two-thirds chance) of staying under 1.5°C will be used up in around 7 and half years.[11, a] 

Hence, the climate challenge can be framed as one of limiting total cumulative emissions of CO2.[10,b]

Halting climate change requires human society to stop emitting CO2 rapidly, entirely and forever,[c] or that any emissions are matched by an equal amount of rapid CO2 removal from the atmosphere.[10] There are currently no available or likely available technologies to safely remove CO2 at the scale and timescale needed.[12]  

By far the biggest cause of CO2 emissions is burning fossil fuels for energy[6] (used for electricity and heat production, transport, industry, manufacturing and commerce)[6] Energy is responsible for over 80% of CO2 emissions.[13] Consequently, the climate change problem is principally an energy problem.

To have any chance of staying well below 2°C, there must be a rapid and complete transformation of the global energy system, starting now. In other words, coordinated system change by governments, corporations and international organisations is necessary to halt global warming.

Individual action to cut CO2 emissions is also part of the solution. While insufficient on its own to halt climate change, individual action contributes to system change. By examining our own lifestyle and contribution to climate change and making changes to cut our own carbon footprint, we can influence others and contribute to awareness and conversation. And cutting our own CO2 emissions is not the only action we can take. We can inform ourselves about climate change, its dangers and solutions and use our knowledge to influence others. We can also use our purchasing and democratic choices to encourage and facilitate the systemic change needed to halt global warming. So, while it’s commendable to make personal commitments to cut our environmental footprint, that is only part of what we can do to be part of the solution. 


a. CO2 emissions may fall by up to 7% in 2020 due to the COVID 19 pandemic.[14] This drop is insignificant compared to the long-term accumulation of CO2 in the atmosphere.[15] Hence, the drop in emissions in 2020, unless repeated annually for the next decade, will have no impact on the challenge to stay well below 2°C.[8]  Rising CO2 concentrations – and related global warming – will only stabilise once annual global emissions reach net-zero.[4]

b. Mitigating non-CO2 emissions, such as methane and nitrous oxide, without immediate and drastic cuts to CO2 emissions, will not halt climate change.  However, not reducing non-CO2 emissions in line with CO2 emissions would decrease the available carbon budget and reduce the chances of remaining well below 2°C.[4]

c. To have any chance staying well below 2°C, emissions of CO2 from high income countries need to reach zero by 2035 to 2040, with interim mitigation rates of 10% to 20% per year.[16]


  1. For example, Eunice Foote, John Tyndall and a question of priority 2019. And: On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground, Svante Arrhenius, Philosophical Magazine and Journal of Science Series 5, Volume 41, April 1896, pages 237-276.   
  2. The Basics of Climate Change.  The Royal Society.
  3. Focus on cumulative emissions, global carbon budgets and the implications for climate mitigation targets 2018.  Environmental Research Letters.
  4. Anthropogenic and Natural Radiative Forcing. 2013.  Intergovernmental Panel on Climate Change. 
  5. Atmospheric Lifetime of Fossil Fuel Carbon Dioxide. 2008.  Annual Review of Earth and Planetary Sciences. 
  6. CO2 emissions by fuel.  Our World In Data. 
  7. The Paris Agreement.  UNFCCC. 
  8. Emissions Gap Report 2019.  United Nations Environment Programme. 
  9. IPCC Special Report.  Global Warming of 1.5°C.
  10. Focus on cumulative emissions, global carbon budgets and the implications for climate mitigation targets. 2018. Environmental Research Letters.
  11. That’s how fast the carbon clock is ticking. 
  12. Negative emission technologies: What role in meeting Paris Agreement targets?. 2018.  European Academies Science Advisory Council.  
  13. Global Carbon Project. 2020. 
  14. Global Carbon Project. 2020.
  15. Analysis: What impact will the coronavirus pandemic have on atmospheric CO2. Carbon Brief. 2020. 
  16. Professor Kevin Anderson. A Prescription for the Planet.  2019.  
  1. Climate change: yes, your individual action does make a difference.  2019. Steve Westlake, The Conversation.