Human factors, such as land use and drainage, also play a part in whether heavy rain leads to flooding. Take the UK, for example.
This raises another important point. When it comes to interpreting the results of event attribution studies, it matters what the question is. For example, a study asked whether recent wet summers in northwestern European were a response to retreating Arctic sea ice pdf, p The paper notes that, in a chaotic weather system, the complex dynamics of the atmosphere mean the size and path of a storm or heavy rainfall event has a large element of chance.
This can make it tricky to identify where climate change fits in, potentially underestimating its influence. Higher temperatures mean warmer seas, higher sea levels and more moisture evaporating into the atmosphere.
These are changes that scientists can be more confident in, the authors write, and so should be the focus for attribution studies — rather than looking at changes to circulation patterns in the atmosphere. For example, the paper reexamines an earlier study pdf, p15 that suggested climate change had reduced the chances of the five-day heavy rainfall event that hit north-east Colorado in September Trenberth and colleagues argue that while climate change might not have made the specific weather system that brought the rain more likely, it will have contributed to the sheer volume of moisture in the atmosphere.
While attribution studies of heatwaves are generally more straightforward than storms — as they focus on thermodynamic influences — the type of question they are asking is still important. The Russian heatwave in is a good example of this. One study looking at the severity of the event did not find a role for climate change. Yet another one , which did find an influence, looked at the likelihood of the event.
This apparent contradiction is tackled by a third study that reconciles the other two. It is also important to stress that the absence of evidence for a link to climate change is not the same as evidence of absence. In other words, it does not necessarily mean there was no human influence, just that a particular analysis did not find one.
This is why a single study should never be considered the final word on how climate change influences a given type of extreme weather. Capetonians queue for water at natural springs around the city during the water crisis, January This mixed bag of results reflects the inherent complexity of droughts.
And, again, the specific question matters. Conclusions about the role of climate change in a specific drought could depend on whether a study looks at temperature, precipitation or soil moisture, for example.
While much has been achieved in the field of extreme event attribution in a short space of time, scientists are constantly looking for ways to tailor their work to suit the people who might use it. One major goal since the early days of the field has been to expand extreme event attribution to cover a larger and more diverse geographical area. Where in the world scientists can carry out attribution studies — and for what kind of events — will always be limited by the quality and availability of observed data and appropriate models.
The attribution map highlights, for example, that there are relatively few studies of extreme weather in Africa and South America. But, at the moment, there is also a heavy leaning towards weather events that are local to the modelling groups, or that have a particular scientific interest. Otto explains:. The UK, California and Boulder [in Colorado] are, therefore, studied much more than other parts of the world, but that does not necessarily make them places particularly impacted by climate change.
This means that while the studies carried out so far are indicative of the role climate change is playing in extreme weather around the world, they should not be considered representative of all types of extreme weather everywhere, says Otto. She tells Carbon Brief:. As well as expanding the science to cover different types of weather and more of the world, scientists are getting faster at turning the handle on extreme event attribution studies — sometimes crunching the numbers just days after an event has occurred.
The rapid studies included here are all — bar one — produced by the World Weather Attribution WWA initiative, described earlier. While the WWA individual rapid assessments are not individually peer-reviewed, they are conducted using methods that have been through the peer-review process. As the BAMS report explains:. By conducting the analysis in the immediate aftermath of a weather event, these rapid studies provide almost-real-time information on the climate change influence, rather than having to wait many months for a formal study.
In some cases, these rapid assessments are later published in peer-reviewed journals. But from to the rise has more than doubled to 4. The consequences of that are unimaginable. In temperature terms, will likely be the sixth or seventh warmest on record. But the report also shows that the global temperature record is on course to breach 1C for the first time over a 20 year period.
Follow Matt on Twitter mattmcgrathbbc. Image source, Luis Sinco. In Cyclone Sidr flattened , homes, but a warning system and fortified shelters helped limit deaths to 3, Today restoring coastal mangroves and hillside forests aims to stave off surging seas, landslides, and floods during future storms. The global average temperature in May was the highest on record. To cope, the city of Ahmadabad offered potable water and cooling centers in high-risk areas and trained health aides to treat heat-related illness.
Climate change may not cause a particular storm, but rising sea levels can worsen its impact. In a nine-foot storm surge from Hurricane Sandy hit New York City at high tide, making the water 14 feet higher than normal at the tip of Manhattan. It can lead to surface flooding in rivers and streets that can affect transportation. Heavy rain inundated New York City yesterday afternoon, partially submerging the th St Subway station in Washington Heights, footage shows.
A flash flood watch was in effect for New York City through Thursday night. Other parts of the world have different engagements with the water cycle. They may be concerned about the snow fall or river floods that affect broad areas. And then of course huge parts of the world are concerned about drought. It also affects ecosystems and urban parks. It affects water resources and infrastructure like power plants and roads and buildings.
So in all of these climate factors, we see that more than one sector is affected by these changes. We also see that if you take any specific thing that we care about, like agricultural fields, they are affected by more than just one type of climate change. A specific set of climate conditions can lead to two extremes at the same time.
So for example, heat and drought often go together because as conditions become drier, all of that sunshine, all of that energy, all of that heat goes into warming the air. That is a reinforcing cycle that can make hot and dry conditions even more extreme. And as the climate changes further, these shifts become more pronounced and widespread. This idea that you can go from extreme to extreme very rapidly is giving society this sensation of a whiplash.
This is part of the idea of an intensified water cycle. The water is moving faster, so when a wet condition comes it can be extremely wet.
0コメント