Today, knowing tomorrow’s weather is as easy as opening up the weather forecast app on your smartphone device, tuning in to the local news, listening to nearly any radio station or even doing a simple internet search.
But what about tomorrow’s climate? If you wanted to know what a region’s climate would be like at some future point in time, where would you look?
First, it’s crucial to understand the difference between climate and weather. Most people are familiar with the concept of weather, as it affects everyone’s daily life in some way or another. Weather is defined as the state of the atmosphere over a short period of time, and its influenced by temperature, precipitation, humidity, wind, cloud coverage, albedo, and air pressure. Other factors that determine a region’s weather patterns are vegetation, elevation, time of year, and distance from the sea. The conditions of the weather tend to fluctuate constantly, which is why the weather is always changing. Weather forecasts usually have hourly and daily time intervals.
A region’s climate includes all the features of its weather but is measured over longer periods of time, usually thirty years or longer. Climate can roughly be defined as the behavior of the weather over several decades.
The state of the atmosphere differs from one year to the next and during those years, the weather will go through the cyclical changes of the seasons. No two years’ seasons are exactly alike. One year, spring may be quite rainy in your city, and the next year, less so. To know whether your city’s climate is experiencing is becoming rainier, experts would have to observe the region’s rain trends for thirty or more consecutive spring seasons.
So, what will the climate of the future be like?
Information taken from sediments, satellites, and weather stations from recent decades all point to a warming trend in climates around the world. On top of that, spring seasons have begun to start earlier, glaciers have been retreating, and sea levels are rising and temperature readings taken from ice cores are increasing.
Climatologists also use computer programs called climate models to make climate forecasts. These programs model different regions using data from the present to make estimates and assumptions about future climate shifts, but these assumptions are less reliable than predictions based on real-world data. Therefore, climate predictions are less reliable the further you get into the future.
That said, there are reasons to believe that future the “global warming” trend will continue.
The global warming trend is partly induced by human activities and is being amplified by certain self-reinforcing climatological feedbacks, neither of which is expected to cease any time soon. Hence, some degree of future warming is a certainty.
Human-induced global warming is largely the result of fossil fuel burning and land alteration from agriculture and deforestation. Since the industrial revolution (the transition from producing goods by hand to producing them in mass with machines) humans have been much more influential in long-term weather patterns.
Fossil fuel burning is the leading human contribution to global warming. Fossil fuels are burned are organic substances that are taken from the Earth’s crust, their uses range from energy production to manufacturing. Fossil fuels are essentially the remnants of decomposing organic material that naturally creates carbon- and hydrogen-plentiful compounds (also known as hydrocarbons), which gradually become buried underground through geological processes that compress and heat them over millions of years.
Fossil fuels are burned to meet most human energy needs today. When hydrocarbons are heated, the greenhouse gases trapped within them produce heat energy capable of powering engines and spinning turbines for electricity. (Greenhouse gases, including water vapor, methane, carbon dioxide, nitrous oxide, ozone, and chlorofluorocarbons, are molecules that absorb and emit heat radiation.) The hydrocarbons in fossil fuels are also used to manufacture complex carbon-based polymers used to make plastics, paints, rubbers, electronics, etc.
As useful as fossil fuels are, their greenhouse gas emissions are considered a climate forcing, or radiative forcing. A climate forcing is the change in energy flux in the atmosphere. In other words, climate forcing refers to the factors that bring about direct change in the atmosphere’s net energy composure. As mentioned, greenhouse gases radiate heat, which makes them a climate forcing that adds to the total heat energy in the atmosphere.
Land alteration from agriculture and logging are other human activities that enhance planet-wide warming.
Agriculture takes up about five billion hectares, or 38 percent of the global land surface, according to the United Nations’ Food and Agriculture Organization (FAO). As the global population continues to grow, more space is needed to produce agricultural goods to feed everyone. To create new agricultural space, natural ecosystems have to be converted to farmland suitable for crops. A conversion is a euphemism for burning or clearing. Similarly, logging involves cutting trees or sections of a forest for sale as timber and pulp.
When photosynthetic plants are burned or cut down, much of the carbon stored in trees and plants is released back into the atmosphere again as carbon dioxide (CO2). This means that land conversions and logging are directly linked to carbon dioxide emissions. As mentioned above, carbon dioxide is a greenhouse gas, which forces the atmosphere to heat up.
Note: Photosynthetic plants naturally absorb atmospheric carbon and move that carbon into their roots. That carbon can later be accessed by microorganisms in surrounding soils and eventually is stored deeply in underground sediments, where it can remain for millions of years or longer.
The National Aeronautics and Space Administration (NASA) defines climate feedback as processes that can either amplify or reduce the effects of a climate forcing. By this definition, feedback can be categorized as either positive (those that amplify some initial change) or negative (those that reduce some initial change). In positive feedback effects, the process will be self-reinforcing, while negative feedbacks are self-limiting.
Take for example the relationship between wildfires and carbon dioxide emissions. According to Steven Earle, Ph.D., in his book “A Brief History of Earth’s Climate”, wildfires have multiple positive feedback effects that can lead to larger climate changes. In chapter titled 10, “Tipping Points”, Earle claims that when vegetation is burned, the released carbon reinforces climate change. Carbon released from burned vegetation results in higher carbon dioxide levels and thus more overall warming in the atmosphere, and in turn, more wildfires.
How do wildfires contribute to global warming? Basically, hotter temperatures enhance the likelihood of wildfire occurrences by drying out soils and vegetation. Evapotranspiration-the combination of water evaporation, soil moisture evaporation, and plant transpiration-rids soils, trees, shrubs, and grasses of their moisture. Dried-out plant matter acts as kindling during wildfires and enables the spread of flames.
Earle takes an excerpt from the U.S. Global Change Research Program: “Increased warming, drought, and insect outbreaks, all caused by or linked to climate change, have increased wildfires and impacts to people and ecosystems in the southwestern US.”
There a multiple types of feedback loops across our planet’s climate systems. Arctic Sea-Ice melting, for example, is another example of a feedback loop, whereby melting sea ice gives way to thinner ice which is more vulnerable to melting. Also, sea-ice loss releases methane and carbon dioxide in permafrost. The reason is, large deposits of carbon (from plants and other organic matter that have not fully decomposed in frozen soils) are stored in natural gas deposits and as undersea clathrates in the Arctic. As permafrost melts, bacteria break down that organic matter, which discharges methane and carbon dioxide into the air.
Thawing permafrost caused by warming, then, can lead to greenhouse gas emissions and contribute to further heating.
If you want to know what future climates will look like, you should start by tracking how well the world’s countries are doing in their efforts to cut greenhouse gas emissions across sectors (energy production, agriculture, and manufacturing). Greenhouse gas levels are highly relevant to future climate changes because the atmosphere’s temperature directly responds to the chemistry of the air.
Secondly, the state of the climate itself should be assessed. Each climate has its own unique feedback to the changes that we’re observing today. Many of these feedbacks have already locked us into a future in which further heating will be perpetuated by the heating human activities have already caused.
For more information about specific climate change prediction scenarios, please read The Future Climate Change.