Climate science, Part 2

Climate Science Principle 1: The sun is the primary source of energy for Earth’s climate system.

Earth’s orbit around the sun and seasonality is depicted. Source: NASA

Earth’s orbit around the sun and seasonality is depicted. Source: NASA

Michigan State University Extension and Michigan Sea Grant are actively engaged in addressing issues relating to climate change and its potential impacts on our lives, our communities, and our environment. This article focuses on Climate Science Principle 1, and is Part 2 of the Climate Literacy series.

Principle 1 of the Essential Principles of Climate Science is foundational for understanding our global climate: The sun is the primary source of energy for Earth’s climate system.1  We examine the fundamental concepts relating to this principle below.

We’ve all seen and felt the warming effects of sunlight - it melts the snow on roads and rooftops during winter, and can make beach sand too hot to walk on with bare feet in summer. We can also anticipate that cloudy days will be cooler than sunny days. According to the NOAA Climate Program Office, this is because “sunlight reaching the Earth can heat the land, ocean, and atmosphere. Some of that sunlight is reflected back to space by the surface, clouds, or ice. Much of the sunlight that reaches Earth is absorbed and warms the planet.”

Everything is either gaining or losing energy, including people. We try to conserve energy during winter by wearing insulating clothing, while we opt for shorts and short-sleeved shirts to shed energy during the warm days of summer. We are comfortable and our body temperature is stable when our energy gain equals our energy loss. In this way we resemble the Earth, because “when Earth emits the same amount of energy as it absorbs, its energy budget is in balance, and its average temperature remains stable.”1

We’re all familiar with seasonality, where in the Northern Hemisphere we enjoy long days and warm temperatures in summer, and the opposite during winter. This is because “the tilt of Earth’s axis relative to its orbit around the Sun results in predictable changes in the duration of daylight and the amount of sunlight received at any latitude throughout a year. These changes cause the annual cycle of seasons and associated temperature changes.”1

Michigan schoolchildren learn about the glaciers that helped shape our state’s landscape, and that our state stone is the Petoskey Stone, fossilized coral from an ancient warm sea. Understanding that climate can vary tremendously over time explains how it was possible for Michigan to experience both glaciers and coral formation. These dramatic, long-term climate changes occurred because “gradual changes in Earth’s rotation and orbit around the Sun change the intensity of sunlight received in our planet’s polar and equatorial regions. For at least the last 1 million years, these changes occurred in 100,000-year cycles that produced ice ages and the shorter warm periods between them.” 1

Since our sun is the primary energy source driving Earth’s climate, we might expect climate changes to closely parallel changes in the amount of solar energy reaching our planet. We would anticipate that significant climate warming would be accompanied by a significant increase in solar energy, with the opposite being true as well. “A significant increase or decrease in the Sun’s energy output would cause Earth to warm or cool. Satellite measurements taken over the past 30 years show that the Sun’s energy output has changed only slightly and in both directions. These changes in the Sun’s energy are thought to be too small to be the cause of the recent warming observed on Earth.”1

In the next article in this series, we will consider how climate and climate changes are not driven simply by solar energy, but rather by a complex set of variables.

Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.

1 - NOAA, Climate Program Office

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