Global warming has become a contentious term met with both praise and controversy. Most recently, the phrase has been replaced by the term climate change. While scientists don’t agree on global warming, they do agree that the earth’s climate does change. What that means is interpreted differently by diverse scientific thought.
While many call science an exact, others say that science is an ever-evolving hypothesis. And, the future of the climate is one that has predictions from many scientists, but not all come to the same conclusion.
According to the National Oceanic and Atmospheric Administration (NOAA) website, while greenhouse gases occur naturally in the earth's atmosphere, human activity also contribute greenhouse gases– primarily through burning fossil fuels that release carbon dioxide into the atmosphere. And in the past century, carbon dioxide has increased. The average temperature of the earth also has increased about 1.3 degrees F – a correlation pointed to as proof that man is impacting the earth’s temperature.
Brian Kahn, Ph.D. and atmospheric scientist at NASA’s Jet Propulsion Laboratory, agrees and says the agency’s work shows that on average the earth’s temperature is rising and that can be traced to man and an increasing use of carbon fuels or the release of carbon dioxide into the atmosphere.
However, for Jeff Logsdon, Science and Operations Officer with the National Weather Service Northern Indiana, he believes science proves something much different. While Logsdon does not speak for the National Weather Service – a part of NOAA, he says as a meteorologist, he finds that climate change is a true fact, but that the earth is warming as a whole is not a manmade phenomena or one that will last.
First, the time frame of global warming is a factor that must be considered, Logsdon says. Scientists must look at the earth’s entire history, not just a portion of it. “The past 200 years are just a blink of an eye,” he says.
According to a temperature chart from Logsdon, the earth’s temperatures were in a warming period, the “Medieval Warming Period,” from about 400 AD to around 1100 AD. A cooling period followed, and the “Little Ice Age” was in place from about 1400 AD to about 1800 AD.
Land-based measurements have been kept since the 1800s, which is a relatively short period of time during the earth’s life cycle. Logsdon explains that there is definitely an underlying argument for warming since that time, but that doesn’t mean there’s agreement on cause for that warming.
“The atmosphere tends toward normal, day-by-day, season-by-season, decade-by-decade,” Logsdon says. “Any period where there is unusually warm temperatures is followed by a period of unusually cold temperatures. The atmosphere always tries to balance out and strives for a state of equilibrium.”
To show this, he says to consider what people think as an extreme – it’s because it hasn’t been experienced before in their lifetime. But what if the earth isn’t working its cycle in that same lifetime, he questions.
Kahn of NASA says the earth’s temperature is complicated and must be looked at both at the surface and in the atmosphere. NASA studies the earth’s temperature at both levels to study the climate and for weather forecasting. The decades of record shows both warming of the surface’s temperature, as well as the climate above the earth, he says. In addition, satellite records that have been kept by NASA for more than 30 years also indicate warming temperatures.
“All evidence shows that there is clearly warming,” he says. However, the rate of change on average of 1/10 degree C or 2/10 degree F per decade is not the same everywhere around the world, he adds. There are regions that are warming and others that are not, and some that are cooling. However, on average the temperature is warming, he says.
And, Kahn says, the warming trend can be attributed directly to carbon dioxide. “Humans are largely causing the changes in the climate, which a lot of evidence supports that it is direct and empirical,” Kahn says.
The impact can be seen in the arctic region, where glaciers have melted significantly – one of the most impacted areas. For example, because temperatures are warming in the arctic region, a bark beetle that survives only when temperatures are above freezing is having a longer life cycle and destroying more trees, Kahn explains.
But Logsdon says that the length of the earth’s climate cycles are not known and points to a November 1922 article in the “Monthly Weather Review,” that stated similar findings. “Ice conditions were exceptional. In fact, so little ice has never before been noted, ” the article stated. While some may say that points to a trend, Logsdon says it points to another period of time when warming was happening and man was not using carbon fuels at the rate he is today.
And Kahn admits that there are other impacts on the earth’s temperatures, but says the most significant is carbon dioxide from the increased use of fossil fuels. Other aspects also can impact warming. For example, cloud feedback is still an unknown factor. Kahn says the warming temperatures have affected clouds and an ongoing study may not have results for use. “If clouds reflect light, they may counteract global warming, but if they don’t reflect light, the warming could be amplified,” he explains.
In addition, the results of the recent eruption of the Eyjafjallajökull volcano in Iceland also may not be known for years to come. In the past, significant volcano eruptions have cooled the earth’s temperatures,” Logsdon says.
Nature’s role in climate is much greater than man’s role, Logsdon believes. He points to Mount Pinatubo’s 1991 eruption that resulted in cooling temperatures, and a warming period that immediately followed, attributed to the El Nino.
While Kahn agrees that other factors do attribute to the earth’s changing climate, he believes that science supports that man’s responsibility for the recent warming trend is undeniable.
Scientists continue to study the earth’s climate and temperatures and debate man’s impact and at the same time world leaders debate what policy should be enacted to combat global warming. The question remains, which science should be followed?
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