Some of climate change’s impacts are direct, while others are indirect. Understanding the difference between these two categories is important. It will help us understand how climate change works and what can be done to reduce its impacts.

Defining Direct Impacts

Let’s start with direct impacts. These are measurable changes in Earth’s natural systems caused directly by warming temperatures. They are likely the impacts you think of first, such as rising sea levels, melting ice caps, and shifting rain patterns.

Another set of direct impacts is the increased likelihood — and, often, severity — of some naturally occurring events, such as floods, storms, and wildfires. Not every natural disaster can be clearly linked to climate change. A single wildfire, for example, might have happened whether the world was heating up or not. However, climate change makes the chance of that wildfire happening much greater. It also makes it more likely that the wildfire will be severe. This increased likelihood and severity of natural disasters is a very important kind of direct impact. Even a small increase in the number and severity of natural disasters can mean that many more people are impacted by disasters, and more of our money and energy must be devoted to recovery.

Some important direct impacts of climate change are much harder to detect than disasters. Global warming is altering many natural processes and systems. It is changing plant life cycles and increasing ocean acidification.

Ocean acidification is a change in the chemical composition of our oceans through chemical reactions with carbon dioxide in the atmosphere. Because of human-caused air pollution, the amount of atmospheric carbon has been increasing rapidly. Ocean acidification slows the development of coral reefs and is a major cause of the disappearance of these important ecosystems.

Defining Indirect Impacts

Climate change will alter many of Earth’s natural systems and processes. These are not the effects you are most likely to feel. Rather, the direct impacts of climate change will cause less obvious changes to the everyday systems we rely upon for our food, housing, and security. We call these changes indirect impacts because they are the result of climate change interacting with our human systems.

Picture this: Climate change has increased the frequency and length of droughts in a region, a direct impact. In turn, these droughts have caused multiple crop failures and reduced freshwater availability — indirect impacts. Because the amounts of food and water have decreased, people in the region, especially kids, have become malnourished and dehydrated. This is another indirect impact. This makes them more likely to develop a disease, another indirect impact. People are also more likely to fall sick with water-borne diseases because they are forced to drink unclean water, yet another indirect impact.

A single direct impact of climate change can result in many indirect impacts. Other types of indirect impacts include increased heat- and cold-related illnesses, respiratory problems, damage to infrastructure and housing and disruption to supply chains. All of these things can lead to increased costs, community unrest, political conflicts, and migration.

The different effects of climate change can interact and multiply their impact on a community. For example, poor health, economic stress, and social instability caused by climate change might combine to cause a political conflict or war over resources. A single community might find itself experiencing poor water quality, physical health issues, and damaged infrastructure at the same time. When direct and indirect impacts come together, the results can be dramatic.

But Why Differentiate?

If all these impacts are the result of climate change, why do we need to make a distinction between indirect and direct? Because these categories can help us understand the problems and identify different solutions for each one.

Direct impacts can easily be understood, tracked, and even predicted by climate scientists through climate models. Understanding direct impacts is quite clear. The way to prevent them is also clear. To lower their chance of happening, we must lower our greenhouse gas emissions. Greenhouse gases trap heat in the upper atmosphere, which causes average global temperatures to rise. The buildup of greenhouse gases is mostly caused by burning fossil fuels like oil, coal, and natural gas, which are used for things like electricity, heat, and transportation. Reducing the use of fossil fuels is the major way to prevent continuing climate change.

Dealing with indirect impacts is more complicated. There are many different ways in which indirect impacts can be reduced and addressed. These solutions fall into two broad categories. First, we can reduce indirect impacts by reducing direct impacts through the decreased use of fossil fuels. Second, we can adapt to climate change. For example, we can design housing to be naturally cooler in the summer. As communities around the world face the impacts of climate change, adaptations will become increasingly important. They will help us maintain our way of life while protecting human health and well-being.