Climate Change refers to long-term shifts in temperatures and weather patterns
In order to take action on climate change, it is important that we have a sound understanding of its causes. By doing this, we can act differently to reduce these impacts and understand how human society may have to adapt, or operate differently, in order to sustain the conditions needed for human flourishing.
You may have heard that climate change is a natural Earth process. While there are “natural” sources of climate change, the changes created by these natural occurrences are far too small to be considered a major player in the current climate crisis we are experiencing today.
It is human activity–primarily through the extraction, processing and burning of fossil fuels, like coal, natural gas and oil–that has caused climate change to the scale we are witnessing now. And it will take urgent human action to change course and secure healthy, safe, sustainable and prosperous futures for us all. This article aims to identify the real culprits of climate change, and the role of interconnected Earth systems in compounding the impacts of climate change.
Natural Climate Change
Some shifts in climate can be “natural.” Over the course of Earth’s existence, volcanic eruptions, fluctuations in solar radiation, tectonic shifts, and even small changes in our orbit have all had observable effects on planetary warming and cooling patterns. But are these enough to attribute to our current climate crisis? The short answer is no.
The Sun powers life on Earth, helping to keep the planet warm enough for us to survive. We also know that subtle changes in Earth’s orbit around the Sun are responsible for the comings and goings of past ice ages. But the warming we’ve seen over the last few decades is too rapid to be linked to changes in Earth’s orbit, and too large to be caused by solar activity.
For more than 40 years, satellites have observed the Sun’s solar radiation, or energy output, which has gone up or down by less than 0.1 percent during that period. Since 1750, the warming driven by greenhouse gases (GHGs) coming from the human burning of fossil fuels is over 270 times greater than the slight extra warming coming from the Sun itself over that same time interval.
The same can be said for volcanoes. Volcanic eruptions are often discussed in the context of climate change because they release GHGs into our atmosphere. However, the impact of human activities on the carbon cycle far exceeds that of all the world’s volcanoes combined, by more than 100 times.
“To put it in perspective, while volcanic eruptions do contribute to an increase in atmospheric CO2, human activities release an amount of CO2 equivalent to what a Mount St. Helens-sized eruption produces every 2.5 hours and a Mount Pinatubo-sized eruption twice daily” (NASA).
Tectonic shifts can cause the formation of volcanoes which can erupt, still too small to be attributed to the change in climate we are witnessing today.
The change in the Earth’s temperatures and weather patterns over the last few decades is far too large to be attributed to these natural phenomena.
Human Induced Climate Change
Scientists overwhelmingly agree that human activity is the main driver of the climate change that we are now experiencing worldwide, primarily due to the burning of fossil fuels like coal, oil and gas. Additionally, deforestation for logging and development has led to the widespread destruction of forests, wetlands and other natural resources that store carbon dioxide and prevent it from being released into the atmosphere. (These kinds of resources are called carbon sinks).
Burning fossil fuels generates greenhouse gas (GHG) emissions that act like a blanket wrapped around the Earth, trapping the sun’s heat and raising global average temperatures. Coal, oil and gas development lead to GHG emissions at every stage of their production and consumption, not just when burned as fuel, but as soon as we drill a hole in the ground (or seabed) to begin extracting them.
And what exactly are these greenhouse gases?
- Carbon Dioxide, CO2: Accounting for almost 80 percent of global human-induced emissions, carbon dioxide sticks around in our atmosphere for quite a while. Once it’s emitted into the atmosphere, 40 percent still remains after 100 years, 20 percent after 1,000 years, and 10 percent as long as 10,000 years later. (Carbon dioxide’s lifetime cannot be represented with a single value because the gas is not destroyed over time, but instead moves among different parts of the ocean, atmosphere, and land. Some carbon dioxide is absorbed quickly, but some will remain in the atmosphere for thousands of years.)
- Methane, CH4: Methane only persists in the atmosphere for around 12 years, but it is much more potent in terms of the greenhouse effect. In fact, pound for pound, its global warming impact is almost 30 times greater than that of carbon dioxide over a 100-year period. While methane can come from natural sources like wetlands, more than half of all global methane emissions come from human activities like natural gas production and livestock-based agriculture.
- Nitrous Oxide, N2O: Nitrous oxide is a powerful greenhouse gas: it has a global warming potential (GWP) that is around 270 times that of carbon dioxide on a 100-year time scale, and it remains in the atmosphere, on average, a little more than a century.
- Fluorinated Gases: Emitted from a variety of manufacturing and industrial processes, fluorinated gases are man-made. There are four main categories: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3). Although fluorinated gases are emitted in smaller quantities than other greenhouse gases, they trap substantially more heat. Indeed, the GWP for these gases can be in the thousands to tens of thousands, and they have long atmospheric lifetimes, in some cases lasting tens of thousands of years.
- Water Vapour: The most abundant greenhouse gas overall, water vapour differs from other greenhouse gases in that changes in its atmospheric concentrations are linked not to human activities directly, but rather to the warming that results from the other greenhouse gases we emit. Warmer air holds more water. And since water vapour is a greenhouse gas, more water absorbs more heat, inducing even greater warming and perpetuating a positive feedback loop. (It’s worth noting, however, that the net impact of this feedback loop is still uncertain, as increased water vapour also increases cloud cover that reflects the sun’s energy away from the earth but holds heat in at night.)
Once fossil fuels have been extracted, refined, processed and transported, major sources of its human consumption include: electricity and heat production, agriculture and land use, Industry (manufacturing, construction, food processing), transportation, building operations.
The average temperature of the Earth’s surface is now about 1.1°C warmer than it was in the late 1800s (before the industrial revolution) and warmer than at any time in the last 100,000 years. The last decade (2011-2020) was the warmest on record, and each of the last four decades has been warmer than any previous decade since 1850.
Earth System Feedback Loops
Many people think climate change mainly means warmer temperatures. But temperature rise is only the beginning of the story. Because the Earth is a system, where everything is connected, changes in one area can influence changes in all others.
The previous section noted the impact of deforestation on carbon sinks:
Basically, forests, swamps, and other wetlands have a natural capacity to collect and store carbon dioxide, reducing the amount left in the atmosphere. But when we cut down forests and reclaim swamplands, then that carbon sink capacity is eroded and often reversed: all the carbon contained in the forests is released into the atmosphere when chopped down. Therefore, deforestation makes climate change even worse.
Feedback loops are more nuanced than this connection, like an intricate stack of dominoes, where one falling creates a reaction that knocks down another and then another and another. Similarly, wildfires and melting glaciers can lead to more wildfires and melting glaciers.
Positive feedback loops occur when a change in one part of the system (like heat), causes changes in the same direction in other parts of the system (more heat). These misleadingly “positive” loops can make climate change worse, whereas negative feedback loops can help to mitigate climate change. Negative feedback loops occur when a change in one part of the system (e.g. increased water vapour/cloud cover) causes changes in the opposite direction in other parts of the system (less heat absorption on Earth).
In this way, melted summer ice in the Arctic (which would usually reflect the Sun’s heat via the albedo effect–negative loop), melts away to reveal the much darker ocean surface of the Arctic, which instead absorbs the sun’s heat, increasing the global warming potential of the seas.
Conclusion
While small amounts of natural climate change has existed over Earth’s history, human activity, through fossil fuel extraction and consumption, is the primary driver of the climate change that we have been experiencing over the past many decades for the first time in human history. And because the Earth is an interconnected system, a change in one place can trigger changes in other parts of the system that exacerbate or worsen the impacts of climate change.
Understanding these root causes is integral to taking action on reducing greenhouse gas emissions and other damaging human activities, as well as preparing for the impacts to come as we adapt to the changes and dynamics already at play.
Author: Alicia Richins
Sustainable Impact Strategist | SDG Champion | Climate Justice Advocate | Climate Futures Writer
