By now, we’ve all heard about climate change. We may have also heard that animal agriculture contributes to climate change. However, before we talk about whether we should care about the greenhouse gas emissions from the livestock industry, we first need to discuss whether we should care about climate change at all. Many people have many different opinions on these topics. But what does science say? Is climate change real? Are humans causing climate change?
What is climate change?
Weather and climate are different. Weather includes the short term atmospheric events occurring at one particular location. The weather changes every day. On some days the weather can be cold and rainy, and the next day it can be warm and clear skies. Climate however, is the long-term state of our atmosphere. Usually, the climate is fairly constant and only changes slowly. If we look at historical trends in the climate, we can predict the future states of the climate. However, predicting the weather is much harder. Predicting the weather is similar to boiling water and trying to determine the location of all of the bubbles. Because the bubbles are part of a complex system and the position of each bubble depends on many variables, our predictions are less accurate. In contrast, predicting the climate is similar to estimating the average temperature of the water as it heats over time. Because the water represents a larger system, we can more consistently and accurately predict its temperature. Another way to look at it, is that the weather is similar to our mood and the climate is similar to our personality. It is difficult to predict mood on any given hour or day. However, our personalities are more consistent over time. Furthermore, just like our personality influences our mood, the climate influences the weather. The climate can change for a number of reasons, such as volcanic eruptions, changes in sunlight intensity, changes in the Earth’s orbit, or changes in the concentration of greenhouse gases in the atmosphere.1,2 Climate change isn’t just about temperature, it’s about a change in many of Earth’s systems.
What is the greenhouse effect and global warming?
The Earth’s atmosphere acts similarly to a greenhouse. There are various types of gases in the atmosphere. Some of these are called greenhouse gases because they trap heat in the atmosphere. Solar radiation must first pass through the atmosphere before it reaches the Earth’s surface. Some of this solar radiation is reflected back into space. However, as solar radiation is relatively high in energy, it can easily penetrate through the atmosphere. The Earth’s surface absorbs some of this radiation and emits it back into the atmosphere as infrared. However, this radiation is less energetic than before. Greenhouse gases can absorb this low energy radiation well. The more greenhouse gases there are in the atmosphere, the more energy the atmosphere absorbs, and the less energy escapes into space. As a result, the Earth stores more heat and hence becomes warmer. So, if that is the case, are greenhouse gases bad? In fact, greenhouse gases have a very important role to play. Without greenhouse gases, the Earth’s average temperature would be about -18°C, which is of course not suitable for many living beings.3 Greenhouse gases themselves are not evil. However, if the correct balance of these gases in the atmosphere is not maintained, problems arise. We need to keep greenhouse gas concentrations within the Goldilocks range.
Are humans causing climate change?
From pre-industrial times until now, the world’s average temperature increased by 1.1°C. The period between 2015-2019 was the hottest on record .4 However, as I mentioned before, the climate is always changing, so could today’s warming just be part of a natural process? Since the Earth is so large, can humans have any affect on the planet?
Approximately 97% of climate change scientists agree that humans are causing global warming. However, various industries and the media have still claimed that climate change is not caused by humans and have presented the topic as if it were still being widely debated by scientists. Unfortunately, this message only misleads and sows doubt within the public.5,6 However, scientists are only human and could be wrong, so this consensus is not evidence in and of itself. So how do we know that we are causing climate change? In the points below I summarise the evidence for anthropogenic climate change and address common misconceptions:
- As the human population and technology have increased, our greenhouse gas emissions have also increased. As the concentration of greenhouse gases in the atmosphere has increased, so has the average temperature of the earth.7,8 This correlation is very strong. Earth’s temperature and greenhouse gas concentrations are increasing much faster than in the past.
- Nature emits more greenhouse gases than humans, through processes such as respiration and decomposition.9 So then, do our emissions only have a small effect on the atmosphere? Not quite. In the past, nature’s emissions were reabsorbed and a balance was achieved. However, if humans emit more on top of this, nature cannot absorb the excess emissions quickly enough, and the concentration of greenhouse gases in the atmosphere increases.
- Changes in solar radiation intensity do not explain this large increase in temperature. In fact, in recent times, the sun’s intensity has actually decreased slightly.10,11
- During several periods in the recent past, the average temperature of the earth has decreased. So does this fact disprove global warming? Nope. Short-term fluctuations are expected. If we zoom out and look at the overall trend, we can clearly see a warming trend.12
- Carbon dioxide and methane are common greenhouse gases. The concentration of carbon dioxide in the atmosphere is now 421 parts per million and the concentration of methane 1924 parts per billion.8 1924 parts per billion means that by weight, for every billion parts of air there are only 1924 parts of methane. It may seem like this number is too small to have any effect on the planet. However, our intuition about nature can sometimes be misleading. For example, even if we only consume a small dose of the poison, we can still die. Some molecules can still have a large effect, even at small concentrations.
- The effect of greenhouse gases on global warming can be well explained by physics. Our physics-based models and simulations are complex, have a degree of uncertainty, and have been wrong in the past. However, if we tune the models correctly, then the results match well with measured data.13
Why should we care about climate change?
Whether the climate changes or stays the same, will the Earth be fine in the end? Yes, it will. The Earth is just an object. So, from Earth’s perspective, whatever we do is irrelevant. However, climate change will affect the lives of those living on Earth. Humanity probably will not become extinct due to climate change. However, our lives and the lives of the animals we share this Earth with will become harder.
Warming by just a few degrees may not seem like a big deal. Whether today is 20°C or 22°C doesn’t really matter. Furthermore, if colder countries became hotter, people who live there might even be more comfortable. However, if the Earth warms by 2°C on average, this warming will be more severe in some regions. Everywhere will not warm equally by 2°C. For example, the Arctic is warming more than the rest of the world.14 To make things more complex, because climate change can affect ocean currents and their associated transportation of heat, some regions may actually cool down.15
Increasing the average temperature of the Earth and the concentration of greenhouse gases has negative effects on many systems. Ocean acidity has increased by 26%. Because of this and the warming of the oceans, corals are dying.4 Furthermore, sea level rise is accelerating. At the moment, the sea is rising at a rate of 4 mm per year. This can be a problem for coastal and low-lying regions and cities. The ice in the Arctic and Antarctic is gradually melting.16 Floods, wildfires, droughts, heat waves, and hurricanes are increasing in frequency and intensity. Climate change can also negatively impact crop yields.17,18
But don’t plants need carbon dioxide? Correct. But the concentration is important. We already have enough carbon dioxide in the atmosphere for the Earth’s vegetation. If we increase the concentration, plants will grow better and the Earth will become greener.19 However, this fact doesn’t prove that high concentrations of carbon dioxide aren’t a problem. The extra carbon stored in this vegetation is still less than we emit.
Already, the effects of climate change are occurring earlier and more severely than predicted. Despite this, global greenhouse gas emissions continue to rise, and the concentration of greenhouse gases in the atmosphere continues to increase. Many countries have made agreements to lower emissions. But even if we achieve the agreed goals, by 2100 the average temperature of the Earth may still increase by 2.9-3.4°C. In order to achieve the 2°C warming target, we need to triple our agreed emission reductions. In order to achieve the 1.5°C warming target, our agreed emission reductions need to be five times greater. 16 The difference between 1.5°C or 2°C of warming may not seem significant, but it does have a significant impact on the effects of climate change. For example in the 2°C warming scenario, 2.6 times more people may experience extreme temperatures, an ice-free Arctic may become 10 times more common, the reduction in the populations of invertebrate and plant species may be doubled, the population of insects may be reduced by three times, the sea level may be 15% higher by 2100, 99% of coral reefs may be eliminated, and the reduction in the worlds gross domestic product (GDP) may be 66% larger.20
Climate tipping points are a phenomenon in which the average global temperature goes beyond a certain threshold, which causes further warming. This is an example of a positive feedback loop, or a vicious cycle. For example, as ice sheets melt, sea levels rise. However, ice reflects sunlight into space. So, as the ice sheets melt, less sunlight is reflected and so more heat remains in the atmosphere. This causes the Earth to warm, which further causes the ice sheets to melt even more. Another example is that biodiverse ecosystems such as the Amazon and coral reefs store less carbon as they die off due to climate change. This then goes on to further increase emissions. Similarly, as permafrost melts, microorganisms previously frozen inside the ice can release methane, or the once frozen soils can release carbon. As the planet warms, the probability of crossing these tipping points increases. Crossing one tipping point could cause the climate to cross other tipping points. In this case, even if we stop emitting altogether, the climate could still change rapidly. So we need to limit warming as much as practically possible.15 There is some uncertainty regarding the exact temperature that would trigger each tipping point, but it would be better to take a cautious approach and reduce emissions as soon as possible.
Conclusion
Climate change is a genuine problem and will become an even bigger problem later. Humans are causing climate change via our greenhouse gas emissions. Will the Earth spontaneously catch on fire? Not quite, but climate change will create many environmental, economic, and political problems. Solving this problem now would be easier and cheaper than dealing with the consequences later. Furthermore, future generations who did not cause this problem, will be able to enjoy a better future. For now, at least, the Earth is our only home. In the next post, I will discuss the emissions associated with animal agriculture and whether we should worry about them.
References
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