This is literally the opposite of what a growing body of recent evidence has shown. Research actually showns that rates of global sea level rise have accelerated in recent years (Nerem et al. 2018), and estimates regarding the upper end of plausible further SLR over the coming century have actually increased considerably as the non-linear contribution by continental ice sheets comes into clearer focus (Bamber et al. 2019). So, if anything, sea level rise is becoming more of a problem than previously thought.

Observed spatial trends in global hydroclimate over the past century have been consistent with those expected from human influence in the climate system (Marvel et al. 2019). In many mid-latitude and subtropical regions, this has indeed included an increase in the frequency/intensity of drought (Diffenbaugh et al. 2015; Williams et al. 2020)--but in other regions (such as the Northern Hemisphere high latitudes), this includes an increase in moisture availability and decrease in drought (as expected from climate model simulations). Therefore, it doesn't really make sense to make blanket statements regarding overall global drought trends, since only some places are expected to get drier (and others wetter) in a warming climate.

There is an extensive and growing body of evidence showing that many kinds of extreme weather have increased in magnitude and/or frequency as the climate has warmed. Evidence is strongest regarding increases in extreme heatwaves and extreme precipitation events (Diffenbaugh et al. 2020), but there is also extensive evidence regarding increasing intensity of other physical event types such as droughts, wildfires, and hurricanes (especially in specific regions). Indeed, there is now an entire sub-field of climate science, known as "extreme event attribution," devoted to understanding how climate change is affecting the occurrence and intensity of extreme weather-related events (Swain et al. 202030247-5)).

It is important to note that the purported "study" that is the subject of this article is not actually a study in any meaningful sense of the word. It is written by a single author who is not a physical or climate scientist, contains no previously unpublished data, and has not been peer-reviewed.

This is highly misleading, as it conflates different types of fire (many of which are not wildfires to begin with). Overall trends in area burned globally are strongly driven by decreases in intentional agricultural burning in tropical areas, which is not related to climate change.

In regions where non-agricultural fires occur naturally (including the western United States (e.g., Abatzoglou et al. 2016, Williams et al. 2019, Goss et al. 2020), eastern Australia (Abram et al. 2020), and the Siberian Arctic (Feurdean et al. 2020), for example) there is strong evidence that climate change has already increased the severity and extent of wildfire (Jones et al. 2020).

There is relatively little evidence in either direction at this point in time regarding global or even regional trends in tornado frequency/intensity. This is largely due to sparse and temporally inhomogeneous historical records in the United States, and virtually non-existent records in other regions. There is some evidence of regional shifts in tornado frequency (Gensini and Brooks 2018), and perhaps an increase in overall tornado "power" in the United States (Elsner et al. 2018), but in general there is an absence of strong evidence regarding this claim.

Future projections regarding climate change and tornado risk are of somewhat low confidence, but there is evidence that atmospheric environments favorable for severe convective storms (which are the types of storms capable of producing tornadoes) may increase in the future due to climate warming (Diffenbaugh et al. 2013, Hoogewind et al. 2017)

While is true that there remains no strong evidence for an increase in tropical cyclone (hurricane) frequency on a global basis, there is evidence that the most intense tropical cyclones are indeed becoming stronger (in terms maximum of wind speeds and minimum central pressure (Kossin et al. 2020) and are producing more extreme rainfall (Liu et al. 2019).

In fact, these trends are consistent with predictions regarding tropical cyclone behavior due to global warming: there is a strong expectation that the maximum potential intensity of hurricanes will increase due to rising ocean temperatures, even as the overall frequency of such storms does not change greatly or perhaps even decreases (Knutson et al. 2020).

This is essentially the only scientifically accurate claim I can discern in the entire article.

I cannot speak to this specific statistic, but I emphasize that it is largely irrelevant in context and certainly misleading, since it conflates both climate and non-climate related factors.

There are strong links between climate change and wildfire extent and severity in many regions globally. It's less clear whether there are links between climate change and wildfire frequency, but that's not really the relevant metric here. Instead, climate change is clearly modulating the characteristics of wildfire in many regions--broadly increasing the dryness and flammability of vegetation, and allowing fires to become more intense and to burn more extensive areas.

This is misleading and incorrect as stated. While the legacy of 20th century forest management policies, as well as urban incursion into the wildlands, are indeed relevant in some areas, research has shown that such non-climate factors cannot account for the enormous increase in area burned by wildfire both in the broader American West and California specifically.

In fact, drying of vegetation due to climate change is responsible for about half of the observed increase in Western U.S. forest fire area burned over the past several decades (Abatzoglou et al. 2016). More specifically in California, observed warming and drying more than doubled the occurrence of extreme fire weather conditions between 1979 and 2018--a trend that is attributable to human-caused climate change (Goss et al. 2020)

On the whole, this claim is incorrect. While there are clearly certain types of natural disasters unaffected by climate change (earthquakes and volcanic activity, for example), and certain kinds of disasters for which there is an absence of evidence regarding a detectable influence from climate change (tornadoes, for example), there is a long and growing list of extreme event/disasters types regarding which the scientific literature strongly supports links to climate change. These include, but are not limited to: extreme heatwave intensity and frequency, drought intensity, wildfire extent and severity, and the flood hazards associated with tropical cyclones/hurricanes (both from oceanic storm surge and freshwater flooding associated with heavy precipitation).

As I climate scientist, I am unaware of any scientific research that suggests changes in Earth's climate capable of "annihilating intelligent life" over the next 30 years.

There is plenty of evidence that climate change will pose increasingly existential threats to the most vulnerable individuals in society; to low-lying coastal cities and island nations; to indigenous cultures and ways of life; and to numerous plant and animal species, and perhaps even entire ecosystems.

Such consequences are well-supported by the existing evidence, are already starting to emerge in certain regions, and should be of paramount concern. But even these very dire outcomes aren't equivalent to the "end of human civilization," as is claimed in the report.

It seems that the eye-catching headline-level claims in the report stem almost entirely from these knock-on effects, which the authors themselves admit are "beyond their capacity to model." Thus, from a scientific perspective, the purported "high likelihood of civilization coming to an end by 2050" is essentially personal speculation on the part of the report's authors, rather than a clear conclusion drawn from rigorous assessment of the available evidence.

This is a reasonable title for the piece. While climate change is not the only factor in recent extreme and record-breaking heat, it is an important and pervasive one. The notion that climate change is "supercharging" heat extremes is an accurate one.

These statements have much more robust support that the previous one.

This statement is overly broad. Attribution of regional mean precipitation trends is still a challenging task in most places, with some exceptions.

The field of "extreme event attribution" has indeed become much more prominent in recent years. This is a result of a combination of better modeling and analysis tools, plus a longer period of observed climate data from which to draw conclusions. While it is not possible to make these kind of attribution claims for all types of extreme weather events, it is increasingly true that this has moved from the margins to the relative mainstream of climate science.

There have indeed been several recent publications suggesting that certain high-amplitude jet stream patterns have been occurring more frequently in recent years. There are also some hints that this could be related to enhanced high-latitude warming, but the potential causal linkages remain the subject of considerable ongoing scientific debate. At this point, there's not yet consensus that the Arctic is a "likely" culprit, although it certainly is a suspect.

This is accurate. So-called "atmospheric blocking" has occurred frequently this summer, and has historically been associated with extreme temperature and precipitation events.

There is indeed scientific evidence that each of these types of extreme events is increasing (or will increase) in a warming world. However, the evidence is strongest for heatwaves and heavy downpours.

Both of these statements are correct, and collectively emphasize two important points. First, the increasing frequency and intensity of heat extremes does indeed validate model-based and theoretical predictions from decades ago. Second, those same climate models suggest that what is today an extraordinary heat event could indeed become a "typical" temperature in future summers, depending on how much additional carbon society emits in the coming decades.

This section is somewhat confusing, but in any case 123F is not the hottest recorded temperature on Earth. This error probably stems from April of this year, when Pakistan likely set a new global temperature record for the month of April: https://www.nytimes.com/2018/05/04/world/asia/pakistan-heat-record.html

While it is true that the oceanic current known as the Gulf Stream keeps western Europe milder than it would otherwise be, it actually makes the region warmer than it would otherwise be. So the relationship is actually opposite to what is stated here.

Here again: the implication is that the widespread spatial distribution of this particular heat event makes it characteristic of global warming. This is not a correct inference from climate science. Instead, it is the sustained long-term trend toward increased frequency/intensity of such events that links global warming to heatwaves in aggregate. (e.g., http://www.pnas.org/content/114/19/4881)

This "key point" does not correctly convey the linkage between global warming and heatwaves. The implication here is that the widespread spatial distribution of this particular heat event makes it characteristic of global warming. This is not a correct inference from climate science. Instead, it is the sustained long-term trend toward increased frequency/intensity of such events that links global warming to heatwaves in aggregate. (e.g., http://www.pnas.org/content/114/19/4881)

While it is true that global warming is contributing to the increased frequency/intensity of global heatwaves in general, it is misleading to claim that it is singularly "to blame" for the present heat extremes.

"Ever" is a long time, and it's not clear this is strictly true for the entire length of Earth's history. But there is strong evidence that this statement is true for all human-relevant timescales: in other words, the rate of CO2 emissions caused by humans is unprecedented since the age of the dinosaurs (i.e., at least 66 million years ago).

This is an important point. "Global mean temperature" (GMT) is a pretty abstract quantity, since any particular location on Earth is likely to experience it. Instead, GMT serves as a useful indicator of how much the Earth's climate has changed overall. While a helpful statistical construct, it masks that fact that the Earth is warming much faster than the global average in some regions (over land, in the Arctic) than in others (over the oceans).

This is a good way to describe the difference in language. It would also be reasonable to say that global warming (the increase in Earth's average temperature) causes climate change (shifts in the location/frequency/intensity of weather patterns). In practice, the two terms are often used somewhat imprecisely and interchangeably (even in the scientific literature).

The question of whether global warming will affect the frequency of hurricanes is indeed an open one, and research continues. There is stronger evidence, however, that warming will increase the maximum "intensity ceiling"/intensification rate of the strongest storms, the maximum rainfall associated with tropical cyclones, and the magnitude of oceanic "storm surges" that occur in an era of rising seas.

Indeed, there is now observational evidence that global warming has already increased the likelihood and magnitude of extreme heat and intense downpours across much of the globe.

This is a reasonable short answer to an extremely challenging scientific question.

This accurate statement succinctly summarizes decades of scientific research across a wide range of disciplines.

As the author correctly notes, the underlying chemistry dates back to the late 1880s.

Indeed.

The title itself is hyperbolic--there's not really a plausible climate change scenario in which the Earth becomes truly uninhabitable (even in the "six degrees of warming" scenario the author explores). That's not to downplay the very real and very large threat to human lives, economies, infrastructure, ecosystems, and species--and the author does a good job cataloging many of these later in the piece. But taken literally, the title implies a future bleaker than is warranted by existing scientific evidence.

It is quantitatively true--and often under-appreciated--that the likelihood of a "worse than expected" climate future is actually higher than a "better than expected" one. That is: the distribution of climate outcomes is not symmetrical, and as others have previously pointed out, "uncertainty is not our friend:" (i.e., http://www.huffingtonpost.com/michael-e-mann/the-fat-tail-of-climate-change-risk_b_8116264.html)

I'm not aware of any scientific evidence for this claim. There has been some work investigating global warming and atmospheric environments conducive to severe thunderstorms (and tornadoes), but to my knowledge there are no peer-reviewed studies that investigate changes in either "length" or "width" of tornadoes. In general, the net effect of climate change upon tornado activity/intensity remains uncertain (http://science.sciencemag.org/content/354/6318/1419), with evidence for increasingly favorable atmospheric environments for tornado formation in some regions (http://www.pnas.org/content/110/41/16361.abstract?sid=89f90e2a-c65d-4424-a394-37c4256350e5).

There is indeed evidence that the frequency and intensity of floods/droughts is increasing over much of the globe (e.g., http://www.pnas.org/content/114/19/4881.abstract), and will continue to do so as the climate warms. This is not necessarily true universally--there will still be quite a bit of spatial and temporal diversity in the response of precipitation extremes to global warming, even in a six-degree-warmer world. But in general, it's true that there will be dramatically more flood and drought events on a global basis with multiple degrees of warming.

There is indeed evidence that maximum hail size in severe thunderstorms may increase with global warming (even while overall hail frequency may decrease): https://www.nature.com/nclimate/journal/v7/n7/full/nclimate3321.html and http://www.pnas.org/content/110/41/16361.abstract?sid=89f90e2a-c65d-4424-a394-37c4256350e5

This is a plausible claim, especially in a "six degree warmer world:" https://www.gfdl.noaa.gov/global-warming-and-hurricanes/

While there is still some uncertainty regarding the response of tropical cyclones (i.e. typhoons and hurricanes) to global warming, there is now evidence that frequency in many ocean basins may actually decrease, but maximum intensity will likely increase: https://www.gfdl.noaa.gov/global-warming-and-hurricanes/

El Nino events do indeed elevate global temperatures temporarily, and this is partly why global temperatures in 2016 were so extreme. But as the attached plot from NASA GISS shows, temperatures so far in 2017 have still been extraordinarily warm in a historical context and in fact would have been record-breaking if not for the large temperature spike which occurred in 2016. In any case, it is not scientifically meaningful to measure global temperature "trends" over a two year period; the large and statistically significant long-term warming signal overwhelms short-term variations on multi-decadal timescales.

It is indeed true that the Arctic is cold in winter--it's hard to argue with that. But this statement belies the fact that winter 2017 was actually extraordinarily warm by historical standards, and second only to the record-shattering warmth observed just last year (in 2016). The attached plot, created by Zachary Labe and available at (http://sites.uci.edu/zlabe/arctic-temperatures) shows that the -20C temperatures this winter are nearly +10C degrees above the long-term average of -30C! Therefore, the the fact that temperatures were -20C this winter in the Arctic is actually a testament to just how much the Arctic has warmed in recent years.

Arctic sea ice volume has actually exhibited record thinness so far during 2017--beating the previous record years of 2012/2016 by a wide margin. Another nice visualization by Zachary Labe illustrates this quite clearly:

This is not accurate. Substantial evidence suggests that certain kinds of extreme weather events (especially heat waves, droughts, and intense downpours) have already begun to occur more frequently over much of the Earth's surface due to global warming (e.g., Diffenbaugh et al. 2017). Further increases in extremes are likely as the Earth continues to warm, and such increases will most likely become detectable across broader geographic regions and for more event types (e.g. IPCC SREX, 2012).

This statement is false. A wide range of direct measurements (i.e. tidal gauges) and indirect measurements (i.e. gravity monitoring satellites) show that the rate of sea level rise has increased (i.e. accelerated) in recent years (e.g. Dieng et al. 2017).

18 years is generally too short an interval to quantify statistically significant climate trends; nevertheless, warming of both the Earth's atmosphere and its oceans is apparent in observational data between 1998 and 2016..

It is quite clear that this document has been created with the intent to intentionally mislead educators and students regarding the causes, character, and even existence of global warming; as such, it has no place in the classroom.

This is false. The majority (and most likely all) of observed global warming is attributable to human influence upon the climate system (i.e. Dieng et al. 2017).

This is not accurate. The importance of carbon dioxide in mediating the Earth's surface temperature via the greenhouse effect has in fact been known for well over a century (e.g., Arrhenius 1896), and an enormous volume of scientific research over decades has demonstrated that the primary cause of observed global warming is the emission of greenhouse gases by human activities (e.g., most recently, Ribes et al. 2016).

This claim is supported by a wide range of scientific research (e.g., Diffenbaugh et al. 2015, Williams et al. 2015). Record warmth during the recent drought has also been directly implicated in some of the most iconic drought impacts, such as extreme lack of Sierra Nevada snowpack (Belmecheri et al 2016) and a large increase in wildfire intensity (Yoon et al. 2015).

There is a considerable and growing body of scientific evidence (see above references) demonstrating that California will likely experience increasingly large swings between extreme wet and extreme dry conditions. The evidence that climate change has already caused such an increase is somewhat less strong--mainly because there are relatively few extreme events in the historical record from which to draw such conclusions.

Therefore, this statement is imprecise, and may be misleading if it is intended to convey that scientists substantially disagree regarding the likely future increase in California precipitation extremes. Whether such an increase is yet detectable in the historical record is indeed uncertain; there is much greater certainty regarding the likely direction of future change.

The skewed rain-snow ratio this season certainly contributed to some of the precipitation-related impacts this winter. While winter 2016-2017 was not exceptionally warm in the Sierra Nevada, especially relative to recent record-warm years, it was still warmer than average. In middle elevation zones of the Sierra Nevada, precipitation fell as rain rather than snow more often that would have historically been the case--leading to a snowpack that significantly lagged overall liquid precipitation (although both were well above average). (See Dettinger 2017: https://eos.org/opinions/defining-snow-drought-and-why-it-matters)

There is indeed observational evidence that California precipitation extremes--and the atmospheric phenomena that cause them--have occurred more frequently in recent years (e.g., Swain et al. 2016), although that signal has only recently emerged from the "noise" of natural climate variability. There is also an expectation that such swings between extreme dry and extreme wet will continue to become more pronounced as the climate warms e.g., (Diffenbaugh et al. 2015; Wang et al 2015; Yoon et al. 2015, Berg and Hall 2015, Gao et al. 2017).

This claim is somewhat overly confident given the available evidence. Observational studies (e.g., Francis and Vavrus 2015) do indeed suggest that the "waviness" of the jet stream and subsequently the propensity for weather patterns to become more persistent has increased in certain regions and during certain seasons, although this is not universally true. There is also emerging evidence that the rapid warming of the Arctic may be playing a role in creating the conditions favorable for weather patterns to become "stuck in place"--a hypothesis that the new Mann et al. 2017 paper discussed in the article supports. The connections between amplified Arctic warming and mid-latitude weather extremes remain a very active area of scientific research (Overland et al. 2016), however, and considerable uncertainty regarding the magnitude and mechanisms of this effect persist.

This is an accurate and succinct description of the primary hypothesized mechanism involved in the Arctic/mid-latitude weather linkage.

This is an accurate framing of the (sometimes contentious) ongoing scientific conversation regarding linkages between Arctic warming and mid-latitude weather.

The fact that numerous high temperature and low sea ice records are still being exceeded in 2017, despite the lack of El Nino conditions the Pacific Ocean, is indeed a testament to the increasingly strong human fingerprint upon global weather and climate events.

There is indeed observational evidence that melting of the Greenland ice sheet, which contributes to global sea level rise, has accelerated in recent years. While scientists are still intensively investigating the details, it is also true that recent research suggests that the loss of Arctic sea ice will mostly likely influence weather patterns in mid-latitude regions (including much of Europe, Asia, and North America).

A recent reference on this latter point (Screen 2017): http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2924.html

The discussion of extreme Arctic warmth in 2016 here and elsewhere in the article is relevant and accurate. A multitude of high temperature and low sea ice records have been set in the Arctic over the past 12 months.

This section accurately describes major 2016 events that occurred in the Earth system and which most likely would not have occurred without global warming.

This section accurately portrays the overall context of the 2016 record, and that the modest differences between datasets do not change the "big picture" conclusion that the Earth is warming, and that 2016 was an extraordinary year even in that context.

This is an accurate and succinct encapsulation of the overwhelming scientific consensus regarding the existence and causes of global warming.