Climate Corner: Knowns and Unknowns of Climate Change

By Dr. Stephen Vavrus

Widespread flooding. Rising sea levels. Another global temperature record. We are awash in news of extreme weather and climate change, but the topic of climate change has become a political football. The unfortunate result is a perception of greater uncertainty than actually exists.

We would like a simple answer to the simple question, “Is the science settled?”

Here I suggest a more nuanced query: What do we know, what do we think we know, and what don’t we know?

What we know:

• Earth’s climate is changing. The warming trend is more than a century old and unmistakable. Even if one questions older temperature measurements, there are many other indicators of a warming climate. They include increasing ocean sea levels, less snow and ice cover, and earlier flowering of plants.
• Humans have altered the composition of the atmosphere. Ancient air bubbles trapped in polar ice caps dating back hundreds of thousands of years demonstrate that current concentrations of heat-trapping greenhouse gases are well outside natural bounds. Present high concentrations of CO₂ probably last occurred a few million years ago.
• Extreme weather has become more common. Although hurricanes, droughts and heat waves have occurred throughout history, reliable data show weather extremes have become much more widespread and frequent. In the past two decades, extreme weather events in the U. S. have exceeded historical bounds established over the past hundred years.

What we think we know:

• Humans are mostly responsible for recent climate changes. Scientists have searched in vain for explanations besides carbon emissions from burning fossil fuels to explain the recent warming trend. We’ve looked into sunspots, aerosols, land-use changes, and astronomical factors, but the only way we can account for the long-term warming trend is greenhouse gas emissions from human activities.
• Warmer and wetter in Wisconsin. Climate projections are an inexact science, but state-of-the-art computer models clearly depict a warmer and wetter future for our state. We can expect warmer conditions in every season and wetter weather during winter and spring. Fortunately, the buffering influence of Lake Michigan should help temper the rise in summertime heat across Door County.
• More extreme rainfall. Because warm air can hold more moisture than cold air, we expect a pronounced increase in the frequency and intensity of heavy rainfalls. A recent local example occurred in Door County just three years ago, when a storm system dumped five to seven inches of rain in Northern Door.

What we don’t know:

• Will future climate change be gradual or abrupt? Computer models are considered reliable in revealing how different our climate is likely to eventually become, but they aren’t able to predict the precise trajectory of how we will get there. Think of it like the seasonal transitions that take place each year. We know the weather will warm up from winter to spring, but no one knows in January if the upcoming shift will be slow and steady, a sudden jump, or alternating periods of cold and heat.
• Will summers become wetter or drier? While climate models agree that future Wisconsin winters and springs will be wetter, there is no consensus about summer rainfall due to the difficulty of predicting the scattered thunderstorms that typify our summers.
• Will Great Lakes water levels rise or fall? One might expect that a warmer climate with less ice cover will cause more evaporation and lower lake levels. Or instead, that wetter winters and springs will raise lake levels. These alternatives also make climatologists uncertain about future shorelines in Door County, in contrast to the nearly certain rise in ocean levels globally.

So, how should society proceed amid this mix of knowns and unknowns?

This critical question falls outside of science, but as a citizen I know we need to act and I am hopeful we will do so promptly and prudently.

First, renewable energy has surged during the past decade because of huge declines in the cost of wind and solar power. This trend should continue, due to both economics and customer demand. Second, support for economic incentives to transition away from fossil fuels is increasing. California recently extended its cap-and-trade emissions program, and interest is growing among businesses and in Congress for market-based solutions spurred by a carbon fee. Finally, technological advances such as new extraction technology, increasingly popular electric/hybrid cars, and stronger energy efficiency measures have helped to lower America’s net carbon emissions in recent years.

Even greater “game changers” in the future, such as new storage technologies and tidal electric generation, may help to put the brakes on climate change.

Earth Care: A Moral Imperative – Presentations, Dialogue and Small Group Discussions

Co-sponsored by Door County churches and the Climate Change Coalition of Door County

Speakers:  Steve Coleman, retired engineer, addressing the effects of climate change and Pope Francis’ encyclical, and Debra Schneider, Catholic Social Justice Minister and VP Waukesha Green Team

Date:  Saturday, Sept. 16, 2017

Time:  9 am – 3 pm

Cost:  $15, includes lunch

Place:  Calvary Methodist Church, 4650 County E, Egg Harbor

Dr. Vavrus is a senior scientist in the Nelson Institute Center for Climatic Research at the University of Wisconsin-Madison. He uses computer climate models to understand how climate is changing across the Earth, including the Great Lakes region. Dr. Vavrus is an active member of the Wisconsin Initiative on Climate Change Impacts (WICCI) and was an invited speaker at last year’s United Nations Conference of the Parties Climate Change Summit in Morocco.

The Climate Corner is a monthly column featuring a variety of writers from around the state and Door County addressing various aspects of the challenges and opportunities climate change presents. The column is sponsored by the Climate Change Coalition of Door County, which is dedicated to “helping to keep our planet a cool place to live.” The Coalition is always open to new members and ideas. Contact the Coalition at [email protected].