Earlier signs of spring, changes in bird migration, and warming lakes and rivers show climate change impacts are already with us, says the Intergovernmental Panel on Climate Change (IPCC).

The Summary for Policymakers from the Fourth Assessment by the IPCC’s Working Group II was approved overnight in Brussels following a plenary session involving government representatives and scientists from more than 130 countries. The summary sets out the working group’s key policy-relevant findings.

Emeritus Professor Blair Fitzharris of the University of Otago is Convening Lead Author for the Australia/NZ chapter of the report and is in Brussels for the plenary. He says the impacts of climate change are already evident across the globe.

“The working group has looked at a wide body of evidence and concluded that recent regional changes in temperature have had a discernable impact on many physical and biological systems,” said Professor Fitzharris.

The report draws on over 29,000 data series of observed changes. The observed evidence detailed in the report focuses on the most sensitive natural processes, including:

• Enlargement and increase in numbers of glacial lakes;
• Increased ground instability in permafrost regions and rock avalanches in mountain regions;
• Changes to water flows from glacier and snow-fed rivers;
• Warming lakes and rivers in many regions;
• Earlier signs of spring, including leaf unfolding, bird migration and egg laying;
• Changes in habitat of plants and animal species.

The report identifies Africa as one of the most vulnerable continents “because of multiple stresses and low adaptive capacity”. It says in Asia, “more than a billion people” could be adversely affected by decreased freshwater availability by the 2050s, due to climate change and other pressures. And small islands, including those located in the tropics, are “especially vulnerable to the effects of climate change, sea level rise, and extreme events.”

Amongst the striking statements in the report:

• “Many millions more people are projected to be flooded every year due to sea level rise by the 2080s. The numbers affected will be largest in the mega-deltas of Asia and Africa, while small islands are especially at risk.”
• With regard to human health, “Projected climate change is likely to affect the health status of millions of people.”

“The scale of the potential impacts depends crucially on how much warming we get, and that depends on global greenhouse gas emissions. By 2020, between 75 and 250 million people in Africa are projected to be exposed to an increase of water stress due to climate change. Studies assessed for the report indicate a further one degree of warming pushes those numbers up to 350–600 million,” says Professor Fitzharris.
New info puts spotlight on ecosystems

Since the last IPCC Assessment much new information has become available. The new report says “the resilience of many ecosystems is likely to be exceeded this century by an unprecedented combination of climate change, associated disturbances (e.g., flooding, drought, wildfire, insects, ocean acidification), and other global change drivers.” It says roughly 20–30% of species assessed so far “are likely to be at high risk of irreversible extinction” if increases in global average temperature exceed 1.5–2.5 °C.

The IPCC says that after the middle of this century carbon dioxide uptake by terrestrial ecosystems is “likely to weaken or even reverse, thus amplifying climate change.”

Some warming is inevitable. The February IPCC report said that even if we shut off greenhouse gas emissions today, the world is committed to a 0.6 °C rise in global average surface temperature by 2100. Today’s report says “a portfolio of adaptation and mitigation measures can diminish the risks of climate change”.

“We need to adapt now to some inevitable impacts, as well as taking action to reduce greenhouse gas emissions,” says Professor Fitzharris. “The benefits of adaptation are immediate, and are required to reduce vulnerability, but there are barriers, limits, and costs to adaptation.”
Future vulnerability depends on development pathways

There are various possible ways in which the world’s population and economies might develop over the 21st century. These will be a strong determinant of the level of vulnerability to climate change. For example, if economic growth continues apace in South and East Asia, more resources could be directed towards adaptation such as building levees and dykes to protect against flooding and sea-level rise.

But Professor Fitzharris points out that “over the long run, adaptation alone can’t deal with all the projected effects of climate change, even in the richest nations. Eventually adaptation will be insufficient to reduce vulnerability.”