Johanna Hoffman, a member of our Emerging Fellows program detects the causes of climate change in her second blog post. The views expressed are those of the author and not necessarily those of the APF or its other members.
Climate change comes in two forms. There is the kind caused by natural processes, and there is the kind created by humans. The former has been happening for millennia, produced by a range of factors from the sun’s energy output to shifts in the earth’s orbit. Since the late 18th century, however, that type of climate change has been supplanted. The industrial revolution and its innovations in manufacturing, production, transportation, power use, and more has led to rapid increases of pollutants, carbon dioxide and other emissions that trap heat in the atmosphere, known as greenhouse gases. For millennia, atmospheric carbon dioxide had never been above 325 parts per million. By 1950, levels had blown far past. Since then, massive changes in land use, such as the proliferation of parking lots and other paved surfaces, have made land absorb more sunlight, which our increasingly greenhouse gas filled atmosphere cannot adequately release. As a result, global temperatures continue to rise.
Most of this warming has occurred in the past 35 years, with the five warmest years on record all taking place since 2010. Much of this increased heat and greenhouse gas has been absorbed by our oceans. Since 1969, the top 700 meters of ocean water have warmed more than 0.22 degrees Centigrade and taken in 25% of emitted carbon dioxide. While these numbers may not seem drastic, the impacts are significant. The great ice sheets of the Artic, Antarctic and Greenland are melting at unprecedented rates, with some scientists predicting that the Arctic will be completely free of summer ice within fifteen years. This melting is not restricted to the poles. All across the globe, from the Alps to the Himalayas to the Andes and the Rockies, glaciers are retreating. Satellites show that spring snow cover in the Northern Hemisphere has declined over the last half century, with snow melts starting earlier, putting fresh water access for hundreds of millions at risk.
As glaciers have melted and ocean waters have warmed, seas have continued to rise. Today, seas are roughly 8 inches higher than they were in 1900, making many low-lying countries such as Bangladesh and the Maldives increasingly uninhabitable. A deadly side effect of this rising and warming is ocean acidification. As the ocean absorbs atmospheric CO2, it becomes more acidic in its chemistry. Over the last 150 years, the acidity of surface ocean waters has increased by about 30 percent, creating harsher environments for wide swaths of animal life. Cetaceans, fish species, crustaceans and more are all adversely affected by acidic conditions, threatening the lives and livelihoods of all those who rely on our oceans for sustenance and support.
The climatic changes spurring these shifts mean more than melting glaciers and rising seas. They mean that the current fires devastating the entire continent of Australia will become the norm in regions around the world. They mean that heat waves and severe storms will grow in intensity. They mean that floods will grow more frequent and more powerful, leaving more people inundated for longer periods of time. They mean that more drought will threaten more of our food supplies. They mean that the world that we knew is changing into some more unpredictable and more unwelcome to human habitation that we have ever seen before.