EXPLAINER | Climate Change
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Climate Change

The Svínafellsjökull glacier in Iceland. Glacial retreat is among the most highly visible impacts of climate change. Since the early twentieth century, with few exceptions, glaciers around the world have been retreating at unprecedented rates.

The Svínafellsjökull glacier in Iceland. Glacial retreat is among the most visible impacts of climate change. Since the early twentieth century, with few exceptions, glaciers around the world have been retreating at unprecedented rates.

There is overwhelming scientific evidence that the earth is warming at an unprecedented rate and human activities are the main driver. Global leaders have been meeting for decades to address this issue, which threatens both human and natural systems.

The most recent major effort– the 2015 Paris climate agreement — sought to strengthen the global response and avoid the worst effects of climate change, by limiting a global temperature rise in this century well below 2 degrees Celsius above pre-industrial levels.

A stark United Nations report issued in 2018 calls on governments to do even more– and try to keep the warming below 1.5 Celsius. The scientists who authored it concede that there is “no documented historic precedent” for such a rapid transformation of the global economy, but say the world faces myriad crises as early as 2040—including food shortages, extreme weather, wildfires, and a mass die-off of coral reefs—unless greenhouse gas emissions are sharply cut.

According to the United Nations Intergovernmental Panel on Climate Change, the “human influence on the climate system is clear.” The National Oceanic and Atmospheric Administration writes, “human activities have increased the abundance of heat-trapping gases in the atmosphere, which a large majority of climate scientists agree is the main reason for the 1.5°F (0.85°C) rise in average global temperature since 1880.” Major greenhouse gases emitted by human activities include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), Hydrofluorocarbons (HFCs), perfluorocarbons(PFCs) ,sulfur hexafluoride(SF6) and nitrogen triflouride (NF3).

Scientists can also look far back into the past and see how the earth’s climate has changed by examining natural time capsules, such as ice cores, layers of glaciers, ocean sediments, tree rings, and coral reefs. Tiny pockets of air left in ice show scientists a “paleoclimate” record, stretching back more than 800,000 years. It reveals “the current climatic warming is occurring much more rapidly than past warming events,” according to NASA’s Earth Observatory.

Although it has a relatively small share of the global population, Pennsylvania is an energy powerhouse and a major contributor of greenhouse gases.

In 2015, Pennsylvania was the third-largest carbon emitter among states, after Texas and California, according to EIA data. Over the past 110 years, Pennsylvania has seen a long-term warming of more than 1 °C (1.8°F), interrupted by a brief cooling period in the mid-20th century, according to the state’s latest climate impact assessment. The state’s warming trend is expected to continue and be coupled with increased precipitation.




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