Is there a need for Geo-Engineering?

Have you ever spoken to a friend or colleague who is a sceptic of human induced climate change and been questioned about why you believe climate change exists. You stumble through your arguments with statements like, “the planet is getting warmer” and, “there’s more carbon dioxide in the atmosphere now” and afterwards feeling you’ve failed the human race with your poorly formed case for anthropogenic (human induced) climate change. Proving the validity of climate change is particularly important with reference to Geo-Engineering as, if anthropogenic climate change doesn’t exist, why are we even bothering with Geo-Engineering?

So where to begin? Strangely enough, it’s going to start with the two points mentioned earlier – temperature and carbon dioxide (and other greenhouse gases (GHGs)). I intend to begin with the same graph that I used in my introductory blog post as I feel it so clearly shows evidence for human induced climate change. An article by Crutzen and Stoermer in 2000 placed the start of the Anthropocene at the latter part of the 18^th century which coincides with the introduction of James Watts’ steam engine. This is important because we are now looking to see if there have been dramatic climate shifts since this date. Figure 1 shows carbon dioxide concentrations (top line) and Antarctic temperature (bottom line) for the past 650,000 years using records from Antarctic ice cores. Over the period 650,000 years ago – c.5,000 years ago, carbon dioxide levels never surpassed 300ppm (parts per million) and yet the present day level is 380ppm (technically 400ppm in March of this year). Looking at Greenhouse Gases (GHGs) more carefully in recent history (Figure 2) it is clear to see that there has been a dramatic upward trend in Methane (CH₄) and Carbon Dioxide (CO₂) since around 1800. What a surprise that this coincides with Crutzen and Stoermer’s dating of the start of human impact on climate. In less than 200 years, methane levels have doubled and carbon dioxide levels have increased by a third – this cannot just be natural climatic variation over such a short time scale. A strengthening of the case for temperature variation is also that the ten warmest years since records began have occurred since 2000.

Figure 1: Reconstruction of past atmospheric CO2 concentration (top line) and temperature reconstruction for the Antarctic (bottom line).

Figure 2: Atmospheric carbon dioxide and methane levels between the years 1000 and 2000.

Next, I wish to highlight a key paper by Steffan et al. in 2015 on Earth System Trends. Below are parts of some of the figures in the paper that I thought were particularly useful when looking at human induced climate change. By studying Figure 3, the trend in environmental variables is particularly concerning, especially tropical forest lost and terrestrial biosphere degradation. This used in tandem with Figure 4 that shows economic and societal trends shows the link between the two. The year 1950 is marked on every graph highlighting the sharp (almost exponential in some cases) increase after this date. From this, it is clear to see that human activity as represented by population, Real GDP and Primary Energy use, etc. is having a clear impact on many natural environments including the oceans, tropical rainforests and coastal environments. The similarity in trends post-1950 is too hard to ignore.

Figure 3: Environmental trends (1750 - 2010).

Figure 4: Socio-economic trends (1750 - 2010).

It would be a mistake if I did not directly mention the impact of fossil fuels on anthropogenic climate change in this post. It is already well known that the primary source of carbon dioxide is from fossil fuel burning. The global production of fossil fuel energy has increased rapidly since around 1945 from about 1500 Mtoe of energy to just over 10,000 Mtoe in 2010. In addition to this, presently about 80% of the world’s energy is as a result of fossil fuels usage, suggesting that the adding of carbon dioxide to the atmosphere by humans is unlikely to stop suddenly or any time soon. This points to a likely need for Geo-Engineering alongside a decrease in GHG emissions.

So from this there is a strong case for anthropogenic climate change supported by a number of statistics and these prove a need for Geo-Engineering techniques. This means that if you ever meet any climate change sceptics you’ll know exactly what to say!