Why is climate change happening?

Climate change is the gradual warming of our planet caused by human activities. Manufacturing and industrial processes, driving gas-powered cars or flying in an airplane, and generating electricity all release greenhouse gases — including carbon dioxide — into the air. Though greenhouse gases are a normal part of our atmosphere and help keep Earth habitable for humans and other life, the excess greenhouse gases released by humans are trapping extra heat near the Earth’s surface. This is causing global temperatures to rise.

How is the climate changing? 

Climate change globally and in the Pacific Northwest 

Global surface temperatures from 2011-2020 were approximately 1.1ºC (2ºF) higher than pre-industrial times (1850-1900). Studies estimate that virtually all of this warming is the result of human activity. 

Climate in the Pacific Northwest is changing, too. Temperatures are increasing, spring snowpack is declining and sea level is rising for most of the region’s coastline. The Pacific Northwest is projected to warm rapidly during the 21st century. 

With every degree of warming above pre-industrial levels, the risks associated with climate change become more severe. For example, according to the Intergovernmental Panel on Climate Change 2018 Special Report, roughly four billion people are projected to be exposed to heat waves with 1.5ºC (2.7ºF) of warming – while roughly 6 billion would be exposed with 2ºC (3.6ºF). For this reason,1.5ºC and 2ºC of warming are recognized internationally as targets for limiting warming.

The role of climate variability

Natural variations in climate can have a big effect on the climate we expect in any given year. These will continue to be important in the future, offsetting long-term warming in some years and amplifying it in others. For example, the Pacific Northwest will continue to experience short-term cooling trends resulting in regional cooling and increases in spring snowpack, even as long-term climate warming trends continue. Two major drivers of Pacific Northwest natural climate variability are El Niño Southern Oscillation (ENSO) (also known as El Niño/La Niña) and the Pacific Decadal Oscillation (PDO).

How can we stop the climate from continuing to warm?

As long as more carbon dioxide is added to the atmosphere than is removed, as is currently the case, global temperatures will continue to increase. To stop the climate from continuing to warm, we have to reach net-zero greenhouse gas emissions. But even if we were to reach net-zero emissions tomorrow, we would continue to see some amount of warming because of the changes we have already put in motion. It may take 20-30 years to see the effects of mitigation policies on global temperatures. 

The window of time for limiting warming to 1.5°C and 2°C is rapidly narrowing; the Intergovernmental Panel on Climate Change has stated we must reach net zero emissions by 2050 to limit warming to 1.5ºC, and reach net zero by 2070 to limit warming to 2ºC.  We must act quickly to reduce our net greenhouse gas emissions to net zero. At the same time, we must prepare for the impacts of climate change — such as heatwaves, wildfire and flooding — that we know are coming.

To learn more about how climate change will impact the Pacific Northwest, check out the next part of this series: What are the impacts of climate change on the Northwest? 

CLIMATE IMPACTS

Related Resources 

IPCC Special Report on Global Warming of 1.5ºC, 2018

To learn more about the science of climate change, read our 10-page summary report “No Time To Waste.”