Climate change is relentless: Seemingly small shifts have big consequences

Since decades, climate change has been slowly but steadily increasing over time. Although the changes may seem small, they can have huge effects on the world, particularly regionally.
Thomas Lohnes via Getty Images

While effects may seem small at first, they can accumulate over time. These effects have now become so strong that they are causing severe heat waves, droughts and extreme rainfall that it is impossible to ignore.

The United Nations Intergovernmental Panel on Climate Change has released a new report that is even more emphatic: Climate change is a result of human activities such as burning fossil fuels. These effects are quickly getting worse.

The energy imbalance on Earth

Earth's energy imbalance is a great example of climate change. Cambridge University Press is publishing a book about climate science that I wrote.

The Sun constantly bombards Earth with solar radiation, which is approximately 173,600 terawatts. That's 12 zeros. Around 30% of this energy is reflected back into the universe by clouds and reflective surfaces like snow and ice. This leaves 122,100 Terawatts to drive all weather and climate systems, including the water cycle. Except for approximately 460 TW, almost all that energy is reflected back into space.

The problem we are facing is that there is still 460 TW. The planet is warming up because of the excess energy trapped in greenhouse gases. This is called global warming or the Earth's energy imbalance.

Due to the increasing amount of greenhouse gases in our atmosphere, outgoing radiation is declining. This leads to an Earth's energy imbalance that is 460 terawatts. It is indicated which percentage goes into each domain. Kevin Trenberth , CC BY-ND

Comparatively to the natural flow energy through the climate system, the 460 TW seems tiny. It is only a fraction 1 percent. Therefore, it is impossible to go outside and feel that extra energy. However, heat builds up and is having serious consequences.

This puts it in perspective: The global electricity production in 2018 was approximately 2.6 TW. It is approximately 19.5 TW if you take into account all energy consumed around the globe, including heat and industry. The Earth's energy imbalance is immense.

Humans make their mark by interfering with natural energy flow through the climate system. Humans are releasing greenhouse gases, such as carbon dioxide and methane, by burning fossil fuels and cutting down forests.

The atmospheric concentration of carbon dioxide was around 280 parts per thousand of volume before the first industries started burning large quantities of fossil fuels in 1800s. When Dave Keeling started measuring atmospheric concentrations at Mauna Loa, Hawaii in 1958, it was 310 parts/million. These values are now at 415 parts per Million, an increase of 48%.

Increased levels of carbon dioxide cause heating. The human increase is significant in this instance.

Where is the extra energy going?

Over time, measurements have shown that more than 90% of this extra energy goes into the oceans. This causes the water to expand and the sea level to rise.

Around the 1970s, the ocean's upper layer began to warm. Heat reached 500 to 1,000m (1,640 to 3,280ft) depth by the 1990s. It was heating the ocean below 1,500m (nearly 5kft) by 2005.

From 1958 to 2020, the average global temperature change at different ocean depths in zetajoules. The chart at the top shows the difference between the 1981-2010 average and the elevations of 2,000m (6,561 feet). The bottom chart shows the change in depth. The reds are more warm than the average while blues are colder. Cheng et al, 2021, CC BY-ND

From 1992 to 2012, global sea level was rising at an average of 3 millimeters per annum, as measured by satellites and flights. It has been rising at a rate of about 4 millimeters per year since then. It has increased by more than 90 millimeters in 29 years (3.5 inches)

Talk to coastal communities located a few feet above the sea level if 3.5 inches sounds too small. These effects can lead to flooding at high tides in some areas, such as Miami, San Francisco, and Venice, Italy. Hurricanes make coastal storm surges more severe and higher. It is a serious threat to low-lying islands and an increasing cost for coastal cities in the United States.

About 13 terawatts of extra energy goes into melting the ice. Since 1979, the Arctic sea ice has declined by more than 40% in summer. Excess energy can melt land ice such as glaciers, permafrost in Greenland and Antarctica. This puts more water in the ocean and contributes towards sea level rise.

About 14 TW of energy can penetrate land. However, land can absorb 14 TW of energy. The dry season or drought can have a significant impact on the land. This is because plants become more brittle and dry, which increases temperatures and increases the risk of wildfire and heat waves.

More heat has its consequences

The extra heat from the oceans provides an enormous amount of moisture to the atmosphere. This heat is converted to latent heat during storms. It can supersize hurricanes and rainstorms, causing flooding as many people have seen in recent months.

For every 1 degree Fahrenheit (0.55 Celsius), increase in temperature, air can have 4% more moisture. Air above the oceans can be 5% to 15% humidier than it was before 1970. As storms collect excess moisture, heavy rain can cause a 10% increase in rainfall.

This may not seem like much but it energizes the storms and updrafts. The storm lasts longer so suddenly there is an increase of 30% in rainfall. As has been demonstrated in numerous cases of major flooding.

Cyclone Yasa heads for Fiji in December 2020. It was the fourth-most intense tropical cyclone ever recorded in the South Pacific. NASA Earth Observatory

Mediterranean climates are characterized by long and dry summers like in California, Australia, and the Mediterranean. Wildfires can easily be sparked by either natural sources or human actions.

Extreme weather events have been a part of the past, but humans are pushing them beyond their limits.

The straw that broke the camel's back syndrome

While all weather events are driven naturally, human-induced climate changes can have a significant impact on their impacts. The storms can cross thresholds, floods are commonplace, and levees fail to keep them from breaking. Fires can erupt, people are killed, and things can't be fixed.

It's what I call The straw that broke the camels back syndrome.

Despite years of warnings by scientists, there has been little progress in slowing down and stopping the problem and planning for future impacts. We all pay the consequences of inadequate planning.

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This article was republished by The Conversation, a non-profit news site that shares ideas from academic experts. This article was written by Kevin Trenberth of the National Center for Atmospheric Research.

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Kevin Trenberth received grants from DOE, NASA, and NOAA in the past, as well as base funding from NSF.