Changing Climate: What Does It Mean? Part One: Climate vs. Weather

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The Earth’s climate has been changing ever since the planet formed an atmosphere. While some changes are natural and cyclical, some are influenced by human activities, and our awareness of that influence has increased over the past two decades. Top Schneider Electric meteorologists have concluded that recent climate changes are a contributor to a notable increase in weather volatility.

How can climate change impact our weather systems? For starters, it’s important to understand the difference between climate and weather.

One major difference between weather and climate is the measure of time.  Think of weather as ‘what’s happening outside today/tomorrow/later this week’; whereas climate is more ‘what might happen outside now and in the future based on what’s happened in the past?’ The phrase “climate is what you expect and weather is what you get” is very much true here.

While climate is rarely static, there’s a difference between gradual, small changes that allow plants and animals to adapt, and swift change which impact civilizations and the land’s ability to support them. Many datasets show that the temperatures for most areas of the globe have shown an increase over the past 100 years.  There remains much debate around what changes are causing the warming — if it’s primarily a natural occurrence, or if humans can be held responsible for some part of it. The jury is still out on how much influence each has on the current climate evolution.

Natural climate change

The contributors to natural climate change or variability operate on timescales of years to decades and may include cyclical patterns. Random events such as volcanic eruptions produce more sudden, but short-lived changes. Oceanic temperature changes seem to be a major player in influencing the climate pattern with solar changes contributing as well.  Ocean temperature cycles in the equatorial Pacific can produce La Niña and El Niño episodes.  El Niño or La Niña phases can change annually and make different parts of the world colder, warmer, drier or wetter.

Multi-decadal anomalies of ocean temperatures can also have major impacts on temperatures and rainfall patterns over the course of many years or even decades.  A warm cycle returned to the Atlantic Ocean in 1995 and could be responsible for some of the warmth over North America since then. Once the Atlantic returns to a colder phase, the areas once warmed by the cycle will then be colder.

Volcanic eruptions eject particles that can stay in the high atmosphere and affect the climate for up to two years afterwards.  And the sun, like the weather, goes through many cycles.  In these cycles the sun spots can vary greatly between the peak and valley of the cycle.  Our current solar cycle has been very weak compared to recent ones, which might become important if this trend continues. While the link is not well understood, past weak solar cycles produced a colder climate.

Human influence

Two of the most significant ways we might change our climate are through land–use changes and adding greenhouse gases.  Land use can alter the regional climate in a multitude of ways, by urbanization, deforestation and agriculture. Removing trees from the land and putting a city in its place will raise the temperature due to better heat absorption; growth in urbanization will make the temperature rise even more as the city expands.  On the other hand, in agriculture, planting tends to make the soil and air cooler.  Increased run-off from rainfall is another by-product of urbanization and agriculture.

Greenhouse gas emissions are another way that humans can influence the climate.  Greenhouse gases are a group of gases in the atmosphere that block heat from escaping into space. Other gases of note, both natural and man-made, that can trap heat include water vapor (the most abundant), methane (from the decomposition of plants and animal waste) and nitrous oxide (from soil cultivation). Man-made emissions have increased since the Industrial Revolution — mostly due to CO₂, which accounts for 84 percent of the U.S. greenhouse gas emissions since 2011.

CO_2, which accounts for about 4% of the total greenhouse gas proportion in the atmosphere,has a significant impact on trapping heat from escaping into space. Emissions of this gas can last in the atmosphere for up to 400 years. Once introduced, it is only slowly removed, which is why it is of concern. As global population and industrialization grows, the influence that humans have on the climate system could become greater.

Climate change is a challenging topic. Sorting out how much impact humans have  on climate change compared to  natural causes is difficult to measure.  We do know that climate has changed in the past and will continue to change going forward. While it is hard to quantify just how much human behavior alters the natural course of change, it might be more important to look at other trends that have been emerging. That trend is for more volatile and erratic weather patterns.

In our next blog post on Wednesday, we’ll look more at how recent climate change has been affecting weather patterns.

For a free download of our new white paper, “Changing Climate:  What Does It Mean?”, click here.