Measuring Climate Change

Figure 1: Weather balloon with
parachute and radiosonde.

Q: Do you believe in global warming?
A: We are Measuring it.

Guest blog post by Dr. Charlie Paxton, meterologist

We meteorologists have surface temperature measurements all over the world and with continued automation more measurements are being taken as time goes on. We must also consider what is happening above the ground. Weather balloons carry instruments called radiosondes that report temperature, moisture, wind, and pressure as they ascend into the stratosphere. Satellites, both geostationary and polar orbiting, provide a wealth of atmospheric information including global sea level measurements.

Figure 2: El Niño and La Niña patterns (NOAA)

When trade winds from the east blow across the wide expanse of equatorial Pacific Ocean, the top layer of water is pushed westward. In its place, cool water underneath is exposed in what is called upwelling. This cooler water pattern over the equatorial Pacific that may last for months or years is called La Niña. As trade winds relax, the Pacific Ocean water heats up to what is termed El Niño. These changes over vast portions of the Pacific Ocean have global impacts on weather particularly strong El Niño events that lead to warmer than normal years globally.

Figure 3: Natural cycles that affect Earth's
temperature. (Pianka, U. Texas)

I hear from various people that climate change is natural and not man made, and some of that is true. Earth's orbital path varies between 0.00 (circular) and 0.06 (elliptical) on a 100,000-year cycle.

Earth’s tilt varies from 22° to 24.5° on a 41,000-year cycle. The current tilt is 23.44°. Earth's axis of rotation wobbles from Earth's elliptical orbit on a 23,000-year cycle. Because of the Orbital Eccentricity, Tilt, and Spin Axis Wobble, at times Earth receives more solar radiation. 

Figure 4: Temperature and CO2 from Antarctic
ice cores (Earth Sciences New Zealand)

With these cycles in place, gases trapped in Antarctic ice cores show that for the past million years, Earth has been in cycles of warmth for roughly 20,000 years and cycles of glaciation (that some may call ice ages) for 80,000 years where much of earth’s water is frozen, dropping sea levels, and creating more land areas. We have been in a warm cycle for the past 12,000 years. Unfortunately, the natural cycles cannot account for the ongoing temperature increases.

We also have some climate “wildcards”

Deep Ocean Currents are difficult to measure and not well studied but typically contribute to warm and cold cycles of 40-60 years. Volcanic eruptions release ash and sulfuric acid (SO2) that increases planetary reflectivity and causes cooling. Large meteors, like the one that hit the Yucatan area 66 million years in the past have impacted Earth and changed climate. That meteor ejected mass into the atmosphere which cooled the climate and wiped out the warmth-loving dinosaurs.

Figure 5: World population growth
(sciencesource.com)

One of the factors in temperature increase is Global Population. It has doubled in the past 50 years from 4.1 billion people to 8.2 billion people. We are all contributing heat, one way or another. China and India each have over 1.4 billion people. The United States is number 3 with 335 million people. With population growth comes deforestation, urbanization, and heat and greenhouse emissions from machinery.

Figure 6: Thin veil of atmosphere around Earth. (NASA)

The Greenhouse Effect is important. Greenhouse gases trap heat in the atmosphere. Without the greenhouse gases, Earth would be too cold. Sunlight (solar radiation) comes into the atmosphere and towards Earth. Some of the radiation is reflected back to space, some is absorbed as heat. Too much greenhouse gas increases global temperatures. Please consider that the protective atmosphere around Earth is a thin veil. It looks like the atmosphere goes on forever but the atmosphere in which the greenhouse effect occurs is less than 20 miles deep. No wonder, additional greenhouse gases have such an impact.

Figure 7: Global gas emissions by gas. (US EPA)

A 51% increase in Greenhouse gases has occurred since 1990. Of those gases, 76% was carbon dioxide (CO2) which remains, once in the atmosphere, for 100+ years. Methane was second at 16% and remains in the atmosphere for 10 years – but methane is 22 times more powerful than carbon dioxide. Nitrous oxide accounts for 6% of greenhouse gas emissions and has a lifespan of 120 years. These three gases continue to accumulate in our atmosphere.

Figure 8: Comparison of global mean temperature
change among major reporting agencies.
(Berkely Earth)

The global surface temperature record (from six well known institutions going back to 1850) shows warming from 1905 to 1940. From 1940 to 1970, cooling occurred. This was when acid rain from sulfur dioxide emissions became a problem. The problem was solved when the Clean Air Act was initiated in 1970. The sulfur dioxide was also creating cooling. After 1970, temperatures were on the rise again.

Ice cores reveal the CO2 record going back 800,000 years. Until recently (1911), CO2 had never been above 300 ppm (parts per million). Today CO2 is now 428 ppm and rising. This is alarming!

Feedback mechanisms can create runaway scenarios. For example, permafrost in the northern hemisphere contains billions of tons of methane. The warmer atmosphere melts permafrost which releases methane, which warms the atmosphere, which melts permafrost, which releases methane, which warms the atmosphere, and so on and so forth... Atmospheric methane has been increasing since the 1800s.

Figure 9: 2024 record warmth. (NOAA)

Measured temperatures have increased about 2.4˚F (1.3˚C) globally over the past 125 years as the greenhouse gases increase. It is important to realize that 1 degree of temperature increase will begin to melt ice. Going back to 1850, 2023 was the world’s warmest year on record until 2024. The third warmest year was 2025. It has been 49 years since Earth has had a colder than average year. Global atmospheric data from radiosondes also show temperatures warming above the ground in the lower atmosphere. The Arctic region has shown the greatest warming on the Earth

Figure 10: Annual ocean heat content. (NOAA)

Much of our world is covered by ocean. The oceans are also warming. Just like the land temperatures, the ocean temperatures were the warmest in 2024, with 2023 and 2025 the second and third warmest. Warming oceans create a thermal expansion of water. This raises sea levels.

Figure 11: Warming water melts ice
 leading to ice loss.

The most noticeable effect of warmer ocean temperatures is near the north and south poles. Sea ice has been disappearing. Sea ice has a highly reflective quality (high albedo) that reflects the sun’s warming rays upward.

Also, as ice melts, the warm sunlight gets absorbed by the exposed water and thus heats the water. This is another feedback mechanism

Figure 12: Age of Arctic sea ice 2025. (NOAA)

In 2000, Arctic sea ice that was over three years old was sparse, now it is almost non-existent. The lack of sea ice, which acted as a shield against coastal waves, now leads to significant Arctic coastal flooding. Loss of sea ice that sits on ocean waters does not raise sea levels.

Figure 13: Antarctic sea ice minimum
(National Snow and Ice Data Center)

Antarctic sea ice was steady until about 10 years ago. Now we see it rapidly disappearing due to warmer ocean water under the ice. The smallest daily Antarctic sea ice extent occurred in 2024. During 2025, the sea ice had some growth. Less sea ice also means warmer Antarctic temperatures. This leads to instability of huge glaciers around the edges of the continent.

Figure 14: Arctic glacier ice mass change
 (World Glacier Monitoring Service)

Land ice is a different story. The added warmth melts ice on land areas (glaciers). This melted land ice eventually meets the sea. This raises sea levels. Glaciers are melting worldwide and the before and current views are shocking. 

Figure 15: The startling change in Glaciers. (NOAA)

As the glaciers melt and the water runs off, less mass is within the mountain structure. With less weight, this creates a localized rebound of the land area. Greenland is mostly covered with ice, and it continues to lose mass due to melting. The meltwater runs into the north Atlantic Ocean creating sea level rise and appears to be slowing the Gulf Stream.

Figure 16: Global sea level rise of
10.2 inches (260mm). (NOAA)

As I mentioned, the contributors to global sea level rise are melted land ice and thermal expansion of ocean waters. We have seen an increase of ~10.2+ inches (260mm) during the past 140 years. That doesn’t sound like much but much of the human population lives near sea level. Wind driven water during storms inundates homes and businesses.

Figure 17: Key West tide gage. Engineered systems
during the 1970s - 50 years ago, may not
accommodate events in the 2020s. (NOAA)

This Nuisance Flooding is 300% to 900% more frequent than it was 50 years ago. Many structures were developed in zones that were safe 50 years ago. Because of sea level rise, now we are seeing routine sea water flooding from storms in lower lying coastal areas. This flooding that occasionally happened now occurs much more often.

Water vapor is 2/3 of the world’s greenhouse effect 

For every 1.0˚F (0.6˚C) temperature increase, 4% more atmospheric moisture is possible. There we have another feedback mechanism: temperature rises, water vapor increases, more greenhouse effect, temperature rises, water vapor increases, and so on and so forth. This increase in water vapor has increased precipitation from storms. We now have a 40% greater chance of heavy rain events and 10% more rain.

Figure 18: Wavy jet stream leads to more prolonged weather events. (NOAA)

A slower and wavier Jet Stream circulation is another impact of the warming earth. That means that weather systems move slower and create more prolonged impact. That means the impact of rainy periods and dry spells will last longer leading to more rainfall flooding and more drought.

The ocean absorbs carbon dioxide from the atmosphere. This creates carbonic acid which negatively impacts the building blocks shellfish use to grow shells. It is also corrosive to marine organism shells, skeletons, corals, and calcareous plankton.

Figure 19: Extent of ice in the northern hemisphere
during the last glaciation approximately
19,000 years ago. (NOAA)

One more item. The Atlantic Meridional Overturning Circulation (AMOC) (basically the Gulf Stream circulation and deep undercurrents) is weakening. The AMOC is the weakest in 1,600 years. This is due to melting Arctic area ice. Fresh water on the ocean surface is less salty and less dense and doesn’t sink. This slows the AMOC. With less global heat transfer, we could see a premature return to glaciation.

We need to be good stewards of this beautiful planet that we live on. Changes will happen but we don’t want changes to occur so fast that we cannot adapt to them. 

It’s not the change which is inevitable; it’s our adaptation to the rate of change.

Dr. Charlie Paxton

Charles H. Paxton Ph.D. 

Dr. Charlie, born in London England, has travelled globally, and lived in locations from the Aleutians to Panama to Antarctica. He earned degrees in Meteorology and a Ph.D. in Environmental Science/Policy. Dr. Charlie is a Certified Consulting Meteorologist through the American Meteorological Society and a member of the Royal Meteorological Society. He co-authored "Florida Weather and Climate – More than Just Sunshine," and has written more than 50 science articles. Dr. Charlie uses his experience as a former NOAA Science Officer, and consultant to relay the marvels of weather, Earth science, and art.