Are We the Issue? Causes of Climate Change Over the Past 1000 Years
Shifts in climate are a natural part of the Earth’s history, and they have been constantly changing long before humans appeared. Thus, it begs the question: Do we deserve the blame for causing global warming?
Natural Causes of Climate Change
A scientific study, "Causes of Climate Change over the Past 1000 Years," examined potential natural causes of changes to the northern hemisphere’s temperature from 1000 to 1993 [1]. The Little Ice Age (1303–1850) saw global temperatures drop by 2 °C, and this correlates directly with high levels of volcanism (volcanic eruptions) [1]. The release of ash, gases, and other particles from an eruption covers the atmosphere, blocking solar radiation from reaching the surface and thus decreasing the Earth’s temperature. This effect has been seen throughout the years with events such as ‘The Year Without Summer (1816); hence, volcanism is a major contributor to global cooling.
Solar forcing refers to the amount of solar radiation that is absorbed and reflected by the Earth’s atmosphere or surface. This study analysed the relationship between solar forcing and temperature from the past 1000 years through 3 different models, which displayed gradual fluctuations until the late 1800s–1993, when there was a temperature rise [1]. There was also a trend of increased temperature from 1000 to 1300; however, the 3 models vary in their exact results [1].
Solar forcing is heavily influenced by factors such as greenhouse gases (GHG), aerosols, the Earth’s axis, and albedo (radiation reflected); therefore, even though this is a natural process, it can be immensely influenced by human interference.
Furthermore, the joint effects of volcanism and solar forcing contributed to an increase of 0.15-2 °C from 1905–1955; however, this relationship also correlates with global cooling trends [1]. Moreover, GHGs, solar forcing, and ocean-atmosphere variability (ocean heat capacity) conveyed a potential contribution to warming in 1930–1960 [1].
Moreover, alterations in volcanism and CO2 are responsible for temperature increases from the mid-late 1800s to the early 1900s [1].
In addition, thermohaline circulation changes (ocean current movements) have been deemed a secondary factor in climate change over the past 1,000 years [1].
Human Influence
Significant increases in the production of GHGs and aerosols through the burning of fossil fuels heavily align with extreme rises in temperature since the 1900s. Furthermore, the study assesses that only 25% of global warming in the 20th century can be accounted for by natural forces [1], therefore suggesting that humans have contributed to 75% of global warming in this period. Thus, it seems that the recent increases in climate are heavily aligned with the rise of fossil fuel consumption and other unsustainable practices, such as increased rates of deforestation. Further alignments with evidence of human-induced global warming include alpine glaciers retreating in 1850 and the warming of tropical oceans in the late 1800s [1], therefore displaying how the sudden environmental impacts of global warming correspond with the rise of anthropogenic GHGs.
In short, WE are to blame!!
In conclusion, even though nature plays a part in climate change, it is evident that anthropogenic influences are notably responsible for the increase in severity and intensity of global warming in the last 100 years, particularly due to the rising rates of GHGs produced, which correlate with rising fossil fuel consumption and unsustainable practices.
Anthropogenic causes could lead to an unprecedented increase in temperature of 2.5°C by 2100, and this would easily pass the warmest temperature level seen in the past 400,000 years [1].
However, what will happen if temperatures increase by 2°C? What are the consequences of global warming? What are we doing to increase GHGs?
We have many questions, and perhaps science has the answers.
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References
Reference Paper: "Causes of Climate Change over the Past 1000 Years"