Adapting to climate change calls for a local approach, new research shows
Climate change affects every corner of the United States, concludes a new report for the White House. But while the northeast faces heavier rain and greater flooding, hotter and drier weather ups the risk of wildfires in the West. Since climate change’s impacts vary dramatically from place to place, so should the responses, the report notes. As it happens, two more papers this week make a similar point for different parts of the world.
Assessing the climate
Yesterday, the United States government released a brand new National Climate Assessment for 2014 – a detailed look at climate change impacts across the country.
Source: The 2014 US National Climate Assessment
The report warns that climate change’s ecological, economic and social impacts are already being seen across the country and in all sectors. But as well as talking about country-wide trends in temperature and precipitation, it focuses on smaller-scale climatic effects. It says:
“Because human-induced warming is superimposed on a naturally varying climate, rising temperatures are not evenly distributed across the country or over time”
Regional rainfall
Globally, a warmer atmosphere means a shift towards heavier downpours. The map below from the new report highlights how different regions have seen different increases in the frequency of extremely heavy rainfall, however.
Image - NCA_Heavy Rainfall (note)
Percent changes in the amount of precipitation falling during very heavy events (the heaviest 1%) from 1958 to 2012 for each region. Source: The US National Climate Assessment 2014
Northeast and midwest states have seen the largest changes, with more than a 30 per cent increase in precipitation falling as very heavy rain (dark blue). There, heavy downpours frequently exceed the capacity of storm drains leading to flooding, the report notes.
In the southwest, however, the biggest concern is the projected increase in heatwaves, leading to a higher risk of drought, wildfires and pressure on water resources. The table below summarises the major impacts in each of the eight regions the report covers.
Image - NCA_Regional Table (note)
Observed and projected climate change impacts vary across the regions of the United States. Source: US National Climate Assessment 2014.
Patchy warming
Staying with rising temperatures for a minute, another new paper highlights how different parts of the world have been warming up at very different speeds over the past century.
The team of Chinese and US scientists, who examined monthly land surface air temperatures between January 1901 to December 2009, published their findings in the journal Nature Climate Change on Sunday.
Before 1950, the data show a few areas of both moderate warming and weak cooling, mainly scattered around the subtropics either side of the equator. The top left panel of the graph below shows these warming and cooling patches.
Image - Ji Et Al ., (2014) Rate Of Warming Graph (note)
Graph showing how warming rates have evolved in different regions. The picture for 1950 shows scattered patches of moderate warming and weak cooling (top left). By 1980, almost all the global land shows warming (second row, right). Source: Ji et al. ( 2014)
By 1980, except for the weak cooling in the northern tip of Greenland and in the vicinity of the Andes, almost all the global land was warming. The paper says:
“The cooling regions shrank and most of them turned into warming regions with an accelerated pace of warming over the next three decades [from 1950].”
At over 0.4 degrees Celsius per decade, the fastest warming in recent decades has occurred in northern mid-latitudes, where the UK and the US sit. Parts of western Africa, near the edge of the Sahara desert, have also warmed noticeably quicker than other areas.
This study differs from previous ones, which have looked at average warming over the last century in a given area but not whether warming has sped up or slowed down, according to the paper.
The authors do not have an explanation for the quicker and more widespread warming in the northern hemisphere. But they say it’s likely to be tied to atmospheric circulations and more area covered by land.
Climate impact hotspots
A third paper out this week also makes the point that dealing with climate change isn’t a one-size-fits all situation.
Published today in the journal Global Change Biology, the study highlights how overlapping impacts of climate change – such as drought or flooding, declining crop yields or ecosystem damages – create climate risk “hotspots” in parts of Africa. Lead author Christoph Müller from the Potsdam Institute for Climate Impact Research, says:
“We found three regions to be amongst those most at risk in a couple of decades: parts of Sudan and Ethiopia, the countries surrounding lake Victoria in central Africa, and the very southeast of the continent, including most notably parts of South Africa, Mozambique and Zimbabwe”.
Image - Muller Et Al . (2014) Africa HOtspots (note)
Map showing projected hotspots of climate change impacts in Africa by the 2080s. Scale goes from no impact (white) to the most severe (dark red). Source: Muller et al., ( 2014).
Many of these regions have relatively high populations and high poverty rates, which further raises their vulnerability, says the paper. In contrast, Nigeria and the tropical forests of the Congo are likely to be much less affected.
In each location, the likelihood and severity of impacts can be weighed to decide on appropriate adaptation measures, the paper adds.
A global problem, a local solution
Climate change is a global challenge, and it’ll take a global effort to bring emissions down. But the impacts vary greatly over space and time. So whether it’s new ways to manage water supplies or building bigger flood defences, coping with the consequences of climate change will need to be targeted towards changes happening at much smaller scales.