And by the time they turn 50, if globally we had managed to halt our emissions quickly back in the 2020s, the temperature will have begun to stabilise. We’ll still be facing extreme heat, but at a far more manageable level than if we’d done nothing to halt climate change.
The whole section on future climate projections under different scenarios is superbly explained. The information is well delivered and backed up by relevant peer-reviewed literature.
As the temperature has increased, so has the ability of scientists to determine whether specific events are linked to climate change. They can now model how likely a specific event would be to occur under historical conditions, compared to the record temperatures we’re experiencing.
This is an accurate description of event attribution.
When the Emergency Leaders for Climate Action approached the Federal Government in April they were drawing on decades of data showing that fire conditions are getting worse.
The Forest Fire Danger Index (FFDI) does indeed point to worsening conditions. It's worth noting though that it's very hard to characterise bushfire risk using a single index and the FFDI wasn't designed with a changing climate in mind. In general, there is a great deal more confidence in projections for extreme weather like heatwaves than there is for bushfire weather.
So it’s hotter, and there’s a greater risk of bushfires, but has Australia been getting drier? I mean, there were droughts when you were a kid, right? Well Australia hasn’t been getting drier overall, but where the rain is falling is changing and that is already having a big impact.
This is a great way of communicating a more nuanced change in the climate.
Number of days each year where the Australian area-averaged daily mean temperature is extreme. Extreme days are those above the 99th percentile of each month from the years 1910–2017. Source: BOM
The information is clearly displayed and the source of the data is given.
Small increases in average temperature translate to big increases in the number of extremely hot days, and those hot days have a big impact.
This article uses relevant information on extremes to help show readers the impact of climate change through information less abstract than the global temperature.
catastrophic possibilities
The report focusses on possible scenarios very much on the extreme end of what could happen but then claims there's a "high likelihood" of human civilisation ending. These two statements don't fit together.
a "high likelihood of human civilization coming to an end"
This is hyperbole. The scenario constructed in this report does not have a "high likelihood" of occurring in part because it requires a confluence of circumstances coming together. While it's certainly true that climate change will be damaging to society and the environment and many of the consequences will be severe this does not equate to a high likelihood of civilisation coming to an end.
North America suffers extreme weather events including wildfires, drought, and heatwaves. Monsoons in China fail, the great rivers of Asia virtually dry up, and rainfall in central America falls by half.
Projections of extreme events such as these are very difficult to make and vary greatly between different climate models.
NOAA's analysis found last month was the 3rd-warmest April on record globally. The unusual heat was most noteworthy in Europe, which had its warmest April on record, and Australia, which had its second-warmest.Portions of Asia also experienced some extreme heat: In southern Pakistan, the town of Nawabshah soared to a scalding 122.4 degrees on April 30, which may have been the warmest April temperature on record for the globe, according to Meteo France. Argentina also had its warmest April since national records began there in 1961.North America was the one part of the world that didn't get in on the heat parade. Last month, the average U.S. temperature was 48.9 degrees, 2.2 degrees below average, "making it the 13th-coldest April on record and the coldest since 1997," NOAA said.
The article points to several regional records or near-records for heat extremes that occurred near the start of the year.
The increase in the number of warm temperature records has been documented for many regions of the world (e.g. the US: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2009GL040736) and can be attributed to human-caused climate change: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017EF000611.
For the year-to-date, the Earth is seeing its 5th-warmest start to the year.
Now, according to the NASA GISS record, 2018 is likely to be the 4th warmest year on record https://twitter.com/ClimateOfGavin/status/1063106429530333184
Climate scientists use the 20th-century average as a benchmark for global temperature measurements. That's because it's fixed in time, allowing for consistent "goal posts" when reviewing climate data. It's also a sufficiently long period to include several cycles of climate variability.
This is an excellent summary of why the 20th century average is a suitable baseline
The cause for the streak? Unquestionably, it’s climate change, caused by humanity's burning of fossil fuels.
The article very quickly and correctly attributes the cause of the warmth to human-cause greenhouse gas emissions
Scorching Earth: Global warming to blame for all-time heat records being set worldwide, as experts warn stifling temperatures will continue to soar
Without a full analysis of this particular event we can't explicitly blame global warming for it. It is likely that the weather patterns that are bringing this heat have not changed in their frequency too much, but that the temperatures are a little warmer than they would have been under analogous weather patterns in the past.
We are experiencing more heat records in general due to human-caused climate change and this has been shown for many regions of the world.
the kind of extreme heat we saw this past summer will be the norm
Recent research shows that even under the Paris Agreement global warming limits, hot extremes like these will become more common: https://www.nature.com/articles/s41558-018-0191-0 Other research has also demonstrated this to be true across Europe, e.g. https://www.nature.com/articles/nclimate2468
The heatwave has spread across the world
Here and in other places in the article there are unhelpful exaggerations and hyperbole that provide a slightly misleading representation of this event.
the highest temperature ever recorded in Scotland
This record has not been accepted by the UK Met Office, so the record high temperature for Scotland remains 32.9°C in August 2003
The human contribution can be up to 30 percent or so of the total rainfall coming out of the storm
A reference here would have been useful as it's unclear exactly where this number comes from. We know that human-caused climate change can increase both the moisture content of the atmosphere, as described by the Clausius-Clapeyron relation, and the energetics of the storm, as there is increased latent heat release. Both of these climate change-influenced drivers have the potential to cause increased precipitation.
All of this said, a storm like Harvey could have happened even if there was no climate change.
This is an intriguing statement. While it's certainly true that major hurricanes could develop in the Gulf of Mexico and strike places like Houston, it is unclear still whether such a strong system could develop in the absence of climate change. This would be very difficult to answer.
The tropical storm, feeding off this unusual warmth, was able to progress from a tropical depression to a category-four hurricane in roughly 48 hours.
This storm was quite remarkable in its intensification. It does seem likely that the warmth of the surface and sub-surface waters, primarily linked to variability but also with a small climate change contribution, enhanced the storm.
But they say that aspects of the case of Hurricane Harvey—and the recent history of tropical cyclones worldwide—suggest global warming is making a bad situation worse.
This is a reasonable statement. As tropical cyclones are such complex events - the confluence of many factors coming together - it is difficult to estimate the climate change role in such events. However, it is likely that human-caused climate change has worsened aspects of this event as described later in the article.
Global warming under Paris pledges
There is a risk that some people might confuse the term "Paris pledges" with the 1.5- and 2-degree targets that came out of the Paris Agreement.
That’s likely to rise to a range of 137 to 200 days per year.
The article doesn't hide the fact that there is fairly high uncertainty in these projections. This helps the reader understand the confidence in the projected changes.
In this scenario, countries would take some measures, but not drastic ones, to curb emissions — roughly the trajectory of the current pledges under the Paris climate agreement.
The map is based on the medium-emissions trajectory of RCP4.5, which is roughly in line with the combined current pledges from the Paris Agreement. It would be useful if the article noted that this trajectory is not in line with either the 1.5- or 2-degree global warming targets from the Paris Agreement.
This means the global temperature trend has now shown no further warming for 19 years
This is both cherry-picking of the data (starting 1998) and not correct anyway http://www.realclimate.org/index.php/archives/2017/01/there-was-no-pause/
record temperatures brought in 2016 by an exceptionally strong El Niño
Last year the annual global temperature was about 1.1C above a late-19th century baseline but only about 0.1C of this was due to the El Nino, the other 1C is due to human influences.
So while the record occurred in 2016 due to El Nino, most of the anomaly was due to climate change.
even satellite temperatures were showing 2016 as “the hottest year on record”,
Satellite temperature datasets have fewer records than in situ-based global temperature datasets largely because they are considerably more noisy. A lower signal-to-noise ratio results in fewer records.
“The need for concerted action on climate change has never been so stark nor the stakes so high.”
This is a statement that very few climate scientists would disagree with.
The El Niño is now waning
The El Niño itself waned quite a long time ago with neutral conditions by mid-2016. The effects of the El Niño persisted through the year though.
For example, the Arctic heatwaves are made tens of times more likely and the soaring temperatures seen in Australia in February were made twice as likely.
This statement is referring to rapid attribution analyses that were conducted by the World Weather Attribution group (https://wwa.climatecentral.org/).
We found that the Arctic heat of late 2016 was made much more likely by human-induced climate change (although it remains a very unusual event in the current climate).
In another analysis we found the February heatwave in New South Wales was at least twice as likely to occur because of climate change.
the month-to-date in the U.S. has seen a ridiculously lopsided ratio of daily record highs to daily record lows, which is a key indicator of short-term weather variability and, over the longer term, human-caused climate change.
This is an important qualification. We expect in a stationary climate that we would have some periods with more record hot temperatures than record lows and vice versa. Over an extended period of time, in a stationary climate, this ratio would average to be one. It's because this pattern of more record hot than record cold temperatures has persisted over recent decades that allows us to link this trend to climate change.
part of a long-term trend toward more warm temperature records versus cold ones
This paper is the first I'm aware of to highlight this effect over the US: http://onlinelibrary.wiley.com/doi/10.1029/2009GL040736/abstract
Extreme high temperatures were seen from India — where the city of Phalodi recorded temperatures of 51 degrees Celsius (123.8 Fahrenheit) in May, a new national record — to Iran, where a temperature of 53 degrees Celsius (127.4 F) was recorded in Delhoran on July 22.
No direct link with climate change has been drawn here and this is good. For these daily heat records attribution to human-caused climate change is a lot harder than for extremes that occur on longer or larger scales. Indeed, in parts of India, the increase in aerosols due to pollution has counteracted the warming from greenhouse gas emissions so that there is virtually no trend in extreme high temperatures.
“debate” over climate change is “far from settled.”
The use of quotation marks here helps to highlight that Pruitt's views are counter to the consensus of climate scientists.
The warming in the Arctic has really been exceptional
A rapid attribution analysis has found that the extreme temperatures in the Arctic of late 2016 would be extremely unlikely without human-induced climate change https://www.washingtonpost.com/news/energy-environment/wp/2016/12/28/2016s-super-warm-arctic-winter-extremely-unlikely-without-climate-change-scientists-say/?utm_term=.a86459c4802f
“We don’t expect record years every year, but the ongoing long-term warming trend is clear.”
This is a really important point, especially as 2017 is likely to not break the 2016 record. We expect year-to-year variability, so we may not break the 2016 record for a few years, but the overall trend is upwards.
Typically, in such an attribution study, scientists will use sets of climate models — one set including the factors that drive human global warming and the other including purely “natural” factors — and see if an event like the one in question is more likely to occur in the first set of models. Researchers are getting better and better at performing these kinds of studies fast, in near real time. So don’t be at all surprised if we see such a study for the current heat wave event — just as we saw for, most recently, the devastating bleaching of the Great Barrier Reef, which was tied to an extreme marine heatwave off Australia’s northeastern coast.
This is an accurate description of how extreme event attribution studies are conducted.
The U.S. National Climate Assessment found that U.S. heat waves have already “become more frequent and intense,” that the U.S. is shattering high temperature records far more frequently than it is shattering low temperature records (just as you’d expect), and that it is seeing correspondingly fewer cold spells.
This is true and is also consistent with findings from other areas of the world. For example, Sophie Lewis led work that showed in Australia there have been 12 times as many hot records compared to cold records since 2000.
In other words, when a planet warms, the odds shift in favor of more intense or long lasting heat waves. That’s just plain logic.
While it seems intuitive that a general warming would lead to longer heat waves, this isn't necessarily the case. In locations where weather systems cause abrupt endings to heat waves (for example, cold fronts passing over Melbourne can reduce temperatures by more than 20 degrees Celsius in summer) then the general warming of the climate by roughly one degree Celsius isn't necessarily causing heat waves to last longer. In general, the duration of a heat wave is often related to how long a weather system like a blocking high sits in the same location, and for many areas we have not seen significant changes.
And the gist is that when it comes to extreme heat waves in general — heat waves that appear out of the norm in some way, for instance in their intensity, frequency, or duration — while scientists never say individual events are “caused” by climate change, they are getting less and less circumspect about making some connection.
This is certainly true. Over the last few years we've seen more and more attribution statements related to heatwaves (where there is higher confidence in the climate change link compared with other extremes, such as heavy rain events) and scientists have become more confident in making this connection.