Natural vs anthropogenic climate change

Climate change is any change occurring to the planet's climate either permanently or lasting for long periods of time. It is the cumulative total of two related sources: anthropogenic climate change and natural climate change. Anthropogenic climate change is defined by the human impact on Earth's climate while natural climate change are the natural climate cycles that have been and continue to occur throughout Earth's history.^[1]

Natural Climate Change

Earth’s climate has always been driven by the amount of incoming and outgoing energy. Without the influence of humans, the Earth has natural cycles that drive the climate. The major factors contributing to Earth’s natural climate change are determined by the [Axial tilt|Earth's orbit around the sun], the output of energy from our sun, the ocean’s natural cooling and warming cycles and the constant variability in volcanic activity. Another factor to consider are the glacial advances and retreats that occur throughout Earth’s history. In the last 650,000 years, there have been around seven ice ages, the most recent ending around 12,000 years ago.^[2] Since then, the Earth has experienced a glacial advance known as the little ice age, which occurred from the 16th century through to the 19th century. However, earth is still in the natural warming process from this glacial advance and many climate change deniers erroneously claim that this is the cause for the current dramatic climate changes. Although natural climate factors have some effect on the current global warming, they are not as drowned out by the human induced factors.^[1]

Anthropogenic Climate Change

Human induced climate change is directly linked to the amount of fossil fuels burned, aerosol releases and land alteration from agriculture and deforestation.<sup id="cite_ref-no1_1-2" class="reference">[1] The beginning of the Industrial Revolution shows a major spike in temperature levels and climate influences. The product of fossil fuel burning is the emission of a greenhouse gas: carbon dioxide which traps heat. Climate change is generally associated with global warming; however some small areas like the tropical Pacific show that the release of aerosols into the atmosphere the area has actually cooled (or at least warmed much slower than the rest of the world).^[3] Figure 2 and 3 below shows the effect of these climate influences.

 

Figure 2: Carbon dioxide levels over the last 400,000 years have stayed below 300 ppm and skyrocketed from 1950's to present.^[2] Note the climate changed quite a bit before the industrial revolution. Those changes were natural, the current climate change is largely anthropogenic.

Some noticeable evidence occurring from anthropogenic climate change is the overall sea level rise, temperature rise, melting ice sheets and glaciers, increased extreme events such as hurricanes getting stronger and ocean acidification. The oceans naturally rise as glaciers and snow covers melt, however compared to the last century, the rate of rise in the last decade is approaching twice as much.^[2] Figure 3 below shows that the Earth has been warming at a frightening rate for the past few decades, and warming is expected to continue for the rest of the 21st century.

 

Figure 3. Sixty years of global warming.^[4]