View from a climate scientist: IPCC makes clear extreme weather is widespread and severe

As a scientist who studies the Earth’s changing climate, I try to keep up on the latest science. In my own research, we are showing that extreme weather events have been getting more extreme over time. Nonetheless, I found the newest IPCC climate report of what is happening globally surprising. This report (the first installment of Sixth Assessment Report) highlighted the overwhelming strength found in the combination of the evidence throughout our planet showing that climate change is accelerating and that attribution analyses are now able to connect the increasing intensity of extreme events much more fully with the changing climate.

This report dramatically documents that the damages being driven by the changing climate is now widespread and severe. Climate change is fueling heatwaves, amplifying droughts, increasing weather that drives wildfires, supercharging tropical cyclones, increasing extreme rainfall, and driving coastal flooding.

While it is straightforward for a meteorologist to show that a given extreme event is connected to a certain weather pattern, new analysis now almost always show that the changing climate has led to a severity of the event that otherwise would not have occurred previously. What were once very rare events are now becoming more common and the changing climate is influencing our weather in ways humanity has not seen before.

At the same time, observations throughout our planet continue to point to a rapidly changing climate, with strongly increasing trends in extreme events with the type of “extreme” depending on where you live.

As a beginning point, observations of the drivers of the changing climate, the increasing concentrations of carbon dioxide (CO₂) and other well-mixed heat-trapping greenhouse gases (GHG) concentrations, show that these increases are unequivocally caused by human activities. Each of the last four decades has been successively warmer than any decade that preceded it since 1850. Globally, extreme heatwaves now occur five times as often as before, and they will hit 14 times as often if warming reaches 2 degrees Celsius. Globally averaged precipitation over land has likely increased since 1950, with a faster rate of increase since the 1980s.

However, the observations also generally show that the wet are getting wetter and dry are getting drier, leading to more significant floods and droughts. Globally, droughts that used to occur once every 10 years now occur 70 percent more frequently. Human influence is very likely the main driver of the global retreat of glaciers since the 1990s and the decrease in Arctic sea ice area. Human influence very likely contributed to the decrease in Northern Hemisphere spring snow cover since 1950.

It is virtually certain that the global upper ocean (0 to 700 meters) has warmed since the 1970s and extremely likely that human influence is the main driver. It is virtually certain that human-caused CO2 emissions are the main driver of current global acidification of the surface open ocean.

A global rise of sea levels of 6 to 12 inches by mid-century is concern enough, but new risk analyses of sea level rise also point to higher potential risks later in the century than recognized in earlier assessments. However, we do still need to better understand how melting of Greenland and Antarctic ice could change sea levels and affect our planet more generally (e.g., concerns about changes in the jet stream and the Atlantic Meridional Oceanic Circulation and how these could affect weather patterns in North America and Northern Europe).

The complex models of the Earth’s air-ocean-land climate system are already providing solid understanding of important climate processes but also continue to improve, so our understanding of potential future changes in climate continue to become clearer. Models do continue to underestimate the changing trends in extreme events. 

The main issues are what are the people on our planet going to choose as future directions for energy, transportation and land use, the primary drivers of the changing climate — thus a range of future scenarios are examined. Despite moves to transfer some energy use to renewables, uncertainties about melting permafrost and long-term effects of increasing trends for major wildfires leaves the highest scenario still in play.

The magnitude of climate change beyond the next few decades will depend primarily on the amount of heat-trapping greenhouse gases emitted globally and, to a limited degree, on remaining uncertainties in the sensitivity of Earth’s climate to those emissions.

We can definitely slow down climate change, but it will take a concerted effort worldwide to reduce the human-related emissions of carbon dioxide and other heat-trapping gases that are driving these changes. Economic analyses do indicate that it is far cheaper to reduce those emissions than to pay for the ever-increasing impacts. Along with reducing the emissions driving climate change, efforts for adaptation and resiliency are crucial to planning for our future.

We need to stop acting as if climate change is a political issue. The science shows this is an important issue that is affecting all regions of our planet. The real debate should be how we find the right solutions to climate change and make sure we leave a legacy of hope for the future to our children and grandchildren.

The IPCC assessment shows that to avoid widespread catastrophic damage, to limit warming to 1.5 degrees Celsius, carbon emissions need to be cut by half in the next 10 years and carbon pollution will need to be brought all the way down to zero by 2050. There is a very narrow path for securing our future and it is rapidly closing.

Donald J. Wuebbles, Ph.D., is the Harry E. Preble professor of Atmospheric Sciences at the University of Illinois, Urbana. He is an expert in the physics and chemistry affecting the Earth’s climate, as well as analyses of climate impacts on society and ecosystems, plus potential resilience and societal responses.