The science is still out as to how best to reduce the impact of climate change on the largest scale and by the most cost-effective means, but what is known is that there’s no doubt among experts about when climate change may occur. It’s already here.
Here are six signs Earth is warming more rapidly than even some scientists expected.
Hottest years on record
2018 was the fourth-hottest year on record in almost 140 years, according to NASA, making the last five years the hottest in recorded history. The data also show that the warmest years on record have occurred since 2001, confirming for scientists that quickly rising temperatures in a short time span are caused by humans, and are very different from the changing climate during Earth's prehistoric time or during the later ice age.
Rising sea levels
Sea levels have been steadily rising over the last century and, in 2017, global levels were 3 inches higher than the 1993 average when satellite record-keeping first began, according to the National Oceanic and Atmospheric Administration. And 2017 also marked the sixth consecutive year of rising seas, with increases during the last 22 out of 24 years.
Nuisance flooding is now 300 to 900 percent more frequent in many U.S. coastal communities than it was 50 years ago, and scientists now predict global sea levels could rise as much as 8 inches, but no more than 6.6 feet by 2100, NOAA reported.
Permafrost stores billions of tons of carbon, which is at risk of being released back into the atmosphere as permafrost melts.
Permafrost, ground that remains frozen for two or more consecutive years and is 3 to 4,900 feet thick, is already thawing in some places in Alaska and the Arctic. This is a huge concern for scientists because they estimate the world's permafrost holds 1,500 billion tons of carbon, almost double the amount now in the atmosphere, according to Columbia University's Earth Institute. When permafrost thaws, it releases carbon into the atmosphere and could accelerate climate change.
Polar bears depend on sea ice for hunting. As the warming planet reduces the amount of annual sea ice, the polar bears' long term survival is in jeopardy.
Melting glaciers and disappearing sea ice
A warming world is causing mountain glaciers and large ice sheets to shrink, which in turn impacts water resources for people who depend on them and contributes to rising seas. Wildlife that depends on ice for survival are also impacted by the diminishing sea ice in the Arctic.
Melting fresh water from glaciers can also alter the ocean by pushing down heavier salt water and ultimately changing ocean currents.
Most people will notice climate change in the form of more intense heat waves and longer periods of droughts.
More extreme weather
As the global thermostat rises, the planet is already seeing extreme and unusual weather events. Heat waves and droughts are the main way people experience climate change right now, according to the U.S. Global Change Research Program. "Over the past 50 years, much of the U.S. has seen increases in prolonged periods of excessively high temperatures, heavy downpours, and in some regions severe floods and droughts." And those conditions are worsening.
Impact on animals and marine life
Climate change is already having an impact on the world's animals, some worse than others. A United Nations report in 2014 found at that time that the warming planet was already having a "widespread and consequential" effect on plants and animals.
Species already in decline due to rising temperatures include polar bears, coral, North Atlantic cod and Adelie penguins, to name just a few.