US Extreme Weather and Climate Change Dashboard
Detection & Attribution: IPCC AR6 vs. This Site
IPCC AR6 (2021) is the most current, most rigorously reviewed formal climate assessment with a dedicated extreme-events chapter (WG1 Chapter 11, supplemented by Chapter 12's regional detail) -- see the Methodology page for the underlying IPCC detection/attribution definitions this whole site applies. The table below summarizes AR6's North-America-focused finding for each hazard alongside this site's reliable-window verdicts, computed live from the exact same data as each hazard's phenomena page.
Read the "Consistency" column as a qualitative judgment call, not a formal statistical test. AR6's findings are global or continental-regional syntheses of many studies and multiple lines of evidence; this site's findings are single-country, mostly-national-scale metrics. Where this site tracks several alternative metrics for one hazard, every metric's verdict is shown below, not just whichever one happens to agree with AR6 -- a real mismatch in scope or metric definition is reported as "not directly comparable," not silently smoothed over.
| Hazard | IPCC AR6 finding | This site's findings | Consistency |
|---|---|---|---|
| Heat Waves | "It is virtually certain that hot extremes (including heatwaves) have become more frequent and more intense across most land regions since the 1950s." |
| Consistent This site's headline heat-wave metric -- WSDI on NOAA's homogenized nClimGrid-Daily record -- shows a clean detected increase since 1951 (p=0.002), and TXx on the same homogenized record agrees (p=0.022). nClimGrid-Daily's record happens to start in 1951, matching AR6's stated 'since the 1950s' window almost exactly, so this is a direct match: same window, same conclusion. Warm nights (TN90p, raw stations) move the same direction but sit just above the bar (p=0.102), so this site renders no detected change there. This site's own raw, non-homogenized station panels are more mixed -- the bespoke heat-wave index and raw WSDI don't clear this site's detected-change bar over their full 1895-2025 record, and raw TXx shows a detected decrease, because the 1930s Dust Bowl anchors an unusually hot early benchmark for the single hottest day each year. That raw/homogenized gap is a genuine, disclosed dataset dependency, not swept under the 'Consistent' label -- an independent, peer-reviewed analysis using similarly raw, unadjusted station data (Christy 2026, Theoretical and Applied Climatology) reaches a comparable raw-data conclusion, finding modest declines in hot extremes across the same conterminous US since 1899. Read together: on the homogenized data this site treats as authoritative for detection, and over the same window AR6 itself cites, the two agree; on raw station data, they don't -- both real findings on the same underlying stations, not a contradiction once the data source is made explicit. |
| Cold Extremes | "...cold extremes (including cold waves) have become less frequent and less severe [across most land regions since the 1950s], with high confidence that human-induced climate change is the main driver of these changes." |
| Partially consistent On the raw US Historical Climatology Network stations, 2 of 4 cold metrics match AR6 directly: the cold spell duration index and cold nights (TN10p) both show a detected decrease. Frost days show no detected change (p=0.433), and the annual coldest night (TNn) shows a detected INCREASE -- that is, coldest nights getting colder, the opposite of AR6's direction. The homogenized nClimGrid TNn shows no detected change (p=0.264) rather than reproducing the raw increase, the same raw-versus-homogenized split this site discloses for heat waves, and the reason this row reads partially consistent rather than consistent. AR6's statement is explicitly about most land regions globally, not the contiguous US specifically; the companion global dashboard, which tests the same four metrics on a global station network, finds a detected decrease in the two duration-and-frequency metrics and no detected change in the other two -- closer to AR6, and at the scale AR6 is talking about. |
| Severe Convective Storms | "There is low confidence in past trends in characteristics of severe convective storms, such as hail and severe winds, beyond an increase in precipitation rates." |
| Consistent Every metric on this page -- tornado count, tornado days, outbreak size, hail (excluded from trend assessment by design, matching AR6's data-insufficiency framing), and three independent CAPE-based instability proxies from reanalysis -- shows no detected change. Matching AR6's 'low confidence, data insufficient' position across metrics built from entirely different data sources (human storm reports vs. atmospheric reanalysis) is a stronger confirmation than any single metric alone could offer. |
| Flooding | "In North America, peak flow has increased in the northeast US and decreased in the southwest US." "Confidence about peak flow trends over past decades on the global scale is low, but there are regions experiencing increases, including parts of Asia, southern South America, the northeast USA, northwestern Europe, and the Amazon, and regions experiencing decreases, including parts of the Mediterranean, Australia, Africa, and the southwestern USA." |
| Consistent This site's own river-flow metrics -- the headline high-flow index (a single national CONUS-wide index) and annual peak flow (AMS) -- show no detected change over their reliable windows. AR6's own US-specific finding explains why a national index wouldn't be expected to show a clean signal in either direction: peak flow has moved in opposite directions within the country, increasing in the northeast and decreasing in the southwest -- exactly the kind of regionally offsetting pattern that would wash out in a single national index rather than contradict AR6's finding. The separate heavy-precipitation-extremes metric on this page (Rx1day/Rx5day) sits just under the significance bar (p=0.095) but does not clear this site's magnitude-vs-variability check, so it too renders as no detected change. AR6 itself draws the distinction that would matter if it did: precipitation-extreme detection carries meaningfully higher confidence than river-flood detection specifically, because dams, diversions, land-use change, and water management confound the streamflow signal in a way they don't for a single storm's rainfall total. An undetected national river-flow trend, when AR6's own regional evidence shows opposing US trends that would cancel out nationally, is the pattern AR6's own literature would predict, not a contradiction. |
| Drought | "Human-induced climate change has contributed to increases in agricultural and ecological droughts in some regions due to increased land evapotranspiration (medium confidence)." On the other drought types this page also tracks: "Few AR6 regions show observed increases in meteorological drought, mostly in Africa and South America; a few others show a decrease (WSB, ESB, NAU, CAU, NEU, CNA: medium confidence)" -- Central North America (CNA), which covers a large share of the continental US, is among the few regions with an observed decrease. On hydrological drought: "The more limited availability of datasets makes it more difficult to assess historical trends in hydrological drought at regional scale. Increasing (MED: high confidence; WAF, EAS, SAU: medium confidence) and decreasing (NEU, SES: medium confidence) trends in hydrological droughts have only been observed in a few regions" -- none of them in North America. |
| Not directly comparable This page now tracks four measures, one for each of AR6's three drought types plus the operational composite: soil moisture (added September 2026, a direct agricultural measure -- the quantity AR6's agricultural/ecological finding is actually about, where this page previously had only the USDM composite standing in for it), SPEI (a precipitation-evapotranspiration index, the same construction AR6 uses for meteorological drought), the low-flow index (an explicitly hydrological, runoff-based signal), and the USDM D2+ composite itself, whose 26-year record is under this site's 30-year minimum and so renders no verdict. None of the three with a long enough record shows a detected change nationally: SPEI p=0.230 over 131 years, soil moisture p=0.882 over 78, low flow p=0.138 over 69. Adding a direct agricultural measure makes the agricultural row a real test rather than a proxy one, and it comes back negative at the national scale. The scale mismatch remains the reason this row stays 'not directly comparable': AR6's agricultural and hydrological findings are regional (Western North America; and no North American region at all for hydrological drought) while this site computes national indices, which would dilute a real regional signal rather than confirm or refute it. For meteorological drought specifically, AR6's Central North America finding is a genuine, if partial, match: a reported decrease, not increase, is at least directionally consistent with SPEI showing no detected increase here. |
| Winter Storms | "There is low confidence in past changes of maximum wind speeds and other measures of dynamical intensity of extratropical cyclones." Separately: "Mid-latitude storm tracks have likely shifted poleward in both hemispheres since the 1980s, with marked seasonality in trends (medium confidence)." |
| Not directly comparable Fritzen, Lang & Gensini (2021) -- an independent, peer-reviewed NARR-based climatology -- found no significant East Coast bomb-cyclone trend. RSI's own storm catalog is intensity-pre-filtered (64% of its tracks are bomb cyclones, versus ~7% in Fritzen et al.'s unfiltered data), which invalidates a raw count from it as a frequency measure. The peak-wind metric on this page (same pre-filtered catalog, but measuring severity rather than frequency) still shows a detected increase; minimum pressure and the RSI storm count show no detected change. Without a valid frequency metric, this row is better read as not yet a clean test of AR6's intensity-trend finding than as confirming or exceeding it. |
| Tropical Cyclones | "A subset of the best-track data corresponding to hurricanes that have directly impacted the USA since 1900 is considered to be reliable, and shows no trend in the frequency of USA landfall events" (Knutson et al. 2019, cited by AR6) -- a direct, US-specific finding, not just a global proportion-of-intense-storms statement. |
| Consistent The US-landfalling hurricane count on this site shows no detected change (p=0.339) over the same since-1900 window AR6's cited reliable subset uses -- a direct, clean match. ACE, rapid intensification, and peak rainfall also show no detected change, none of which AR6's landfall-frequency statement specifically addresses but none of which contradict it either. |
| Wildfire | "Fire weather conditions (compound hot, dry and windy events) have become more probable in some regions (medium confidence)." AR6 separately cites Abatzoglou & Williams (2016), which attributes approximately 49% of the cumulative 1984-2015 burned-area increase in the western United States to anthropogenic climate change -- one of the report's strongest, most quantified attribution statements for any hazard on this site. |
| Consistent MTBS burned area and both fire-weather (VPD) metrics from an independently-sourced reanalysis dataset show a detected increase -- the most consistently confirmed finding on this site across independently-sourced metrics, directly matching AR6's characterization of Western US wildfire as one of its strongest findings. MTBS large-fire count sits exactly on the 10% bar (p=0.100) and so renders as no detected change; NIFC burned area and season length show none either, both drawn from a shorter record than MTBS. This site does not attempt AR6's ~49% attribution fraction itself -- that requires the model-based attribution step this site's detection-only methodology doesn't undertake. |