Category Archives: AMETSOC

Zeke Hausfather regarding Baselines and Buoys

Zeke Hausfather at And Then There’s Physics regarding Baselines and Buoys.

Posted in American Meteorological Association, American Statistical Association, AMETSOC, anomaly detection, Anthropocene, Berkeley Earth Surface Temperature project, BEST, climate, climate data, climate zombies, denial, geophysics, global warming, Hyper Anthropocene, NOAA, oceanography | Leave a comment

Ductless Minisplits in Blizzard, 2017-02-09

(Updated, 11th February 2017, 16:15 EST) We heat and cool our home with Fujitsu `ductless minisplit` air source heat pumps. But this is New England, and it’s winter. A common question is how do they do under winter conditions? Well, … Continue reading

Posted in American Association for the Advancement of Science, American Meteorological Association, American Statistical Association, AMETSOC, Anthropocene, atmosphere, attribution, being carbon dioxide, carbon dioxide, CleanTechnica, climate, climate change, climate disruption, demand-side solutions, efficiency, global warming, Hyper Anthropocene, marginal energy sources, Massachusetts Clean Energy Center, meteorological models, meteorology, National Center for Atmospheric Research, NCAR, New England, NOAA, nor'easters, oceanic eddies, oceanography, open data, open source scientific software, risk, the right to know, water vapor | Leave a comment

A letter to 45

I received a link to this letter regarding the 27th January 2017 White House Executive Order on visas and immigration from the American Meteorological Society. I am also a member of the American Statistical Association, the Ecological Society of America, … Continue reading

Posted in Adam Smith, American Association for the Advancement of Science, American Meteorological Association, American Statistical Association, AMETSOC, citizenship, compassion, criminal justice, Donald Trump, economics, education, evidence, fear uncertainty and doubt, free flow of labor, Joseph Schumpeter, politics, the value of financial assets | Leave a comment

Why scientific measurements need to be adjusted

There is an excellent piece in Ars Technica about why scientific measurements need to be adjusted, and the implications of this for climate data. It is written by Scott K Johnson and is called “Thorough, not thoroughly fabricated: The truth … Continue reading

Posted in American Association for the Advancement of Science, American Meteorological Association, American Statistical Association, AMETSOC, Berkeley Earth Surface Temperature project, Canettes Blues Band, citizen data, climate data, data science, environment, evidence, geophysics, GISTEMP, HadCRUT4, mathematics education, meteorological models, obfuscating data, open data, physics, science, spatial statistics, Tamino, the right to know, the tragedy of our present civilization, Variable Variability | Leave a comment

`Moving forward on climate change and sustainability`

From WGBH, and hat tip to Environmental Justice TV, includes Dr Gavin Schmidt speaking, who I was especially interested in, and whose talk begins here: Interesting that Dr Schmidt has some gentle criticism of the PBS program NOVA. Whole talk … Continue reading

Posted in American Association for the Advancement of Science, American Meteorological Association, AMETSOC, Anthropocene, bridge to nowhere, Buckminster Fuller, carbon dioxide, climate, climate change, climate data, climate disruption, Ecology Action, environment, Equiterre, fossil fuel divestment, Gavin Schmidt, geophysics, greenhouse gases, Hyper Anthropocene, investment in wind and solar energy, Kevin Anderson, moral leadership, NASA, physics, science, Spaceship Earth, sustainability, the tragedy of our present civilization, the value of financial assets, zero carbon | Leave a comment

`Anecdotes don’t make reliable evidence’

From Katharine Hayhoe, who I deeply respect, and from John Cook (*), scientists and the quantitative community have been scolded that the reason they don’t make headway with the public and the science denier community is because their explanations are too … Continue reading

Posted in American Association for the Advancement of Science, American Meteorological Association, American Statistical Association, AMETSOC, Antarctica, Anthropocene, Arctic, astrophysics, bridge to nowhere, changepoint detection, climate, climate change, climate disruption, disingenuity, ecology, Ecology Action, environment, flooding, floods, fossil fuel divestment, geophysics, glaciology, global warming, greenhouse gases, Hyper Anthropocene, ice sheet dynamics, ignorance, leaving fossil fuels in the ground, meteorology, Minsky moment, Neill deGrasse Tyson, NOAA, oceanography, planning, reason, reasonableness, science, shorelines, the right to be and act stupid, the tragedy of our present civilization, the value of financial assets | Leave a comment

On the recent history of climate science.

Link | Posted on by | Leave a comment

NCAR reports on a teleconnection between the Pacific and continental USA

The National Center for Atmospheric Research (“NCAR”) reports on a newly substantiated teleconnection between positive sea surface temperature anomalies (“SSTA”) in the Pacific and the temperatures over the continental United States (“CONUS”) 50 days later. A teleconnection is: A linkage … Continue reading

Posted in American Meteorological Association, AMETSOC, Anthropocene, atmosphere, attribution, climate, climate data, coastal communities, coasts, dynamical systems, environment, fluid dynamics, fluid eddies, food, forecasting, geophysics, hydrology, Hyper Anthropocene, living shorelines, Mathematics and Climate Research Network, meteorological models, meteorology, National Center for Atmospheric Research, NCAR, NOAA, oceanic eddies, oceanography, open data, Principles of Planetary Climate, sea level rise, U.S. Navy, WHOI, Woods Hole Oceanographic Institution | Leave a comment

Climate Potpourri: Flooding and Solar (both from Ars)

And they who will not be ready, will suffer the economic consequences. Ready for flooding: Boston analyzes how to tackle climate change (That water is a foot deep, previously reported in a post here. Click on image to see larger … Continue reading

Posted in adaptation, American Meteorological Association, American Solar Energy Society, AMETSOC, Anthropocene, Bloomberg New Energy Finance, Boston, carbon dioxide, citizenship, civilization, CleanTechnica, climate, climate business, climate change, climate disruption, climate economics, coastal communities, environment, flooding, floods, fossil fuels, global warming, green tech, greenhouse gases, Hyper Anthropocene, ice sheet dynamics, investment in wind and solar energy, John Englander, Joseph Schumpeter, leaving fossil fuels in the ground, living shorelines, Massachusetts, Massachusetts Clean Energy Center, meteorology, oceanography, resiliency, shorelines, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, sustainability, T'kun Olam, the energy of the people, the green century, the value of financial assets | Leave a comment

Sleeping Giant Awakening

Originally posted on Climate Denial Crock of the Week:
https://twitter.com/johnmyers/status/809097380456865792 Wikipedia: Isoroku Yamamoto’s sleeping giant quotation is a quote by the Japanese Admiral Isoroku Yamamoto regarding the 1941 attack on Pearl Harbor by forces of Imperial Japan. The quotation is portrayed at the very end of…

Posted in adaptation, American Association for the Advancement of Science, American Meteorological Association, American Solar Energy Society, American Statistical Association, AMETSOC, Anthropocene, California, Carbon Worshipers, citizen data, citizen science, climate, climate change, climate data, climate disruption, data science, Donald Trump, ecology, Ecology Action, geophysics, global warming, Hyper Anthropocene, ignorance, Jerry Brown, science, sustainability, the right to be and act stupid, the right to know, the stack of lies, the tragedy of our present civilization | Leave a comment

Global Carbon Dioxide in 3D

Your CO2, my CO2 doesn’t remain with you or me, but mixes broadly and thoroughly over the planet at large. So, we all share responsibility for the damage. Credit: NASA And brought to you by OCO-2.

Posted in American Association for the Advancement of Science, American Meteorological Association, AMETSOC, Anthropocene, atmosphere, carbon dioxide, Carbon Worshipers, civilization, climate, climate change, climate data, climate disruption, corporate litigation on damage from fossil fuel emissions, diffusion, diffusion processes, Donald Trump, dynamical systems, ecology, environment, fluid eddies, geophysics, global warming, greenhouse gases, Hyper Anthropocene, NASA, NCAR | Leave a comment

“Negative emissions” (from ATTP)

Originally posted on …and Then There's Physics:
I went to some Departmental talks recently and discovered that some of my colleagues are researchering possible carbon sequestration technologies. This could be very important, but appealing to negative emission technologies is…

Posted in American Association for the Advancement of Science, American Meteorological Association, AMETSOC, Anthropocene, carbon dioxide, carbon dioxide capture, carbon dioxide sequestration, Carbon Worshipers, clear air capture of carbon dioxide, climate, climate change, climate disruption, differential equations, environment, fossil fuels, geoengineering, geophysics, global warming, greenhouse gases, Hyper Anthropocene, land use to fight, leaving fossil fuels in the ground, liberal climate deniers, Principles of Planetary Climate, quantitative ecology, reason, reasonableness, science, sustainability, the tragedy of our present civilization, the value of financial assets, utility company death spiral, zero carbon | 1 Comment

USN Admiral David Titley (ret)

Posted in adaptation, American Association for the Advancement of Science, American Meteorological Association, American Statistical Association, AMETSOC, Anthropocene, attribution, bridge to nowhere, Carl Sagan, citizenship, civilization, clean disruption, climate, climate change, climate disruption, Dan Satterfield, ecology, fossil fuels, geophysics, Hyper Anthropocene, NCAR, oceanography, science, science education, the tragedy of our present civilization, U.S. Navy, Wally Broecker | 1 Comment

On the rise of the Trumpistas …

Just a couple of things to write about The Obvious. I have written a couple of longer thoughts as Comments, here and here, at … And Then There’s Physics. I reiterate that I don’t believe any voter was hoodwinked, that … Continue reading

Posted in adaptation, American Association for the Advancement of Science, American Meteorological Association, American Solar Energy Society, American Statistical Association, AMETSOC, Anthropocene, atheism, Bloomberg New Energy Finance, BNEF, bridge to nowhere, Buckminster Fuller, Bulletin of the Atomic Scientists, Carbon Worshipers, citizenship, civilization, climate, climate change, climate disruption, climate zombies, coastal communities, consumption, corporate supply chains, cynicism, Daniel Kahneman, denial, disingenuity, Donald Trump, dynamical systems, Equiterre, exponential growth, extended supply chains, Exxon, fear uncertainty and doubt, forecasting, fossil fuels, geophysics, global warming, Hyper Anthropocene, ice sheet dynamics, ignorance, Joseph Schumpeter, Massachusetts, Massachusetts Interfaith Coalition for Climate Action, meteorology, Minsky moment, moral leadership, oceanography, organizational failures, physics, Principles of Planetary Climate, rationality, reason, reasonableness, risk, science, science denier, science education, Scripps Institution of Oceanography, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, temporal myopia, the energy of the people, the right to be and act stupid, the tragedy of our present civilization, the value of financial assets, Tony Seba, wind energy, wind power, Woods Hole Oceanographic Institution, ``The tide is risin'/And so are we'' | 2 Comments

Testimony to MassDEP, M.G.L. chapter 21N, section 3(d) (from the Global Warming Solutions Act)

I testified to the Massachusetts Department of Environmental Protection (“MassDEP”) yesterday regarding means of enforcing limits as required by the Massachusetts General Laws, Chapter 21N, Section 3(d), otherwise known as (a portion of) the Massachusetts Global Warming Solutions Act, as … Continue reading

Posted in adaptation, American Association for the Advancement of Science, American Meteorological Association, American Solar Energy Society, AMETSOC, Bloomberg New Energy Finance, BNEF, Buckminster Fuller, Carbon Tax, citizenship, clean disruption, climate, climate business, climate disruption, coastal communities, coasts, consumption, corporate litigation on damage from fossil fuel emissions, decentralized electric power generation, decentralized energy, demand-side solutions, destructive economic development, distributed generation, ecology, Ecology Action, economics, electricity, electricity markets, energy, energy reduction, energy storage, energy utilities, environment, environmental law, evidence, feed-in tariff, fossil fuel divestment, fossil fuels, gas pipeline leaks, global warming, greenhouse gases, grid defection, Hyper Anthropocene, investment in wind and solar energy, ISO-NE, Joseph Schumpeter, leaving fossil fuels in the ground, living shorelines, MA, marginal energy sources, Massachusetts, Massachusetts Clean Energy Center, Massachusetts Interfaith Coalition for Climate Action, meteorology, methane, politics, public utility commissions, PUCs, rate of return regulation, regulatory capture, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, the energy of the people, the green century, the value of financial assets, Tony Seba, utility company death spiral, wind energy, wind power, zero carbon | 1 Comment

What’s going on in the ocean off the Northeast United States

Hint: Climate change has somethin’ to do with it. Schematic diagram illustrating the component parts of the AMOC and the 26◦ N observing system. Black arrows represent the Ekman transport (predominantly northward). Red arrows illustrate the circulation of warm waters … Continue reading

Posted in American Association for the Advancement of Science, American Meteorological Association, AMETSOC, anomaly detection, Anthropocene, bifurcations, climate, climate change, climate disruption, coastal communities, critical slowing down, dynamical systems, ecology, environment, fluid dynamics, geophysics, global warming, Hyper Anthropocene, John Marshall, meteorology, oceanic eddies, oceanography, physics, regime shifts, science, Scripps Institution of Oceanography, sea level rise, the right to be and act stupid, the right to know, thermohaline circulation, WHOI, Woods Hole Oceanographic Institution | Leave a comment

“Hurricanes, Sea Level, and Baloney” (from Tamino)

Originally posted on Open Mind:
WUWT has a post in which Neil Frank proclaims that Hillary Clinton is no hurricane expert but he is. (Frank’s post was originally published on The Daily Caller, but was reprinted on WUWT with permission.)…

Posted in American Meteorological Association, AMETSOC, climate, climate change, climate disruption, denial, environment, global warming, Hyper Anthropocene, meteorological models, meteorology, model-free forecasting, open data, science denier | Leave a comment

“Getting past grudging precautions: How the next President should address climate change”

Professor David Titley (see also, and here) writes in the online newsletter DefenseOne: Many observers think climate change deserves more attention. They might be surprised to learn that U.S. military leaders and defense planners agree. The armed forces have been … Continue reading

Posted in American Meteorological Association, AMETSOC, Anthropocene, Arctic, Buckminster Fuller, Bulletin of the Atomic Scientists, citizenship, civilization, climate, climate change, climate disruption, climate justice, coastal communities, Eaarth, ecological services, ecology, environment, evidence, fossil fuel divestment, geophysics, global warming, greenhouse gases, Hyper Anthropocene, ignorance, investment in wind and solar energy, leaving fossil fuels in the ground, liberal climate deniers, meteorology, rationality, reason, reasonableness, resiliency, Scripps Institution of Oceanography, the right to be and act stupid, the right to know, the tragedy of our present civilization, WHOI | Leave a comment

The Budget

Certain claims regarding contributions of health programs to the United States federal budget in a debate last night made me curious, and so I checked the figures on this from the Office of Management and Budget. Of special importance to … Continue reading

Posted in American Association for the Advancement of Science, American Meteorological Association, American Statistical Association, AMETSOC, Buckminster Fuller, citizen data, citizenship, climate, climate change, climate economics, climate justice, conservation, consumption, Daniel Kahneman, David Suzuki, destructive economic development, ecological services, ecology, economics, environment, environmental law, Equiterre, George Monbiot, Hyper Anthropocene, Minsky moment, mitigation, population biology, quantitative ecology, Sankey diagram, Scripps Institution of Oceanography, Spaceship Earth, sustainability, the right to be and act stupid, the tragedy of our present civilization, the value of financial assets, Woods Hole Oceanographic Institution | Leave a comment

“BlackRock Investment Fund will include climate change as risk factor for portfolio”

BlackRock, the world’s largest private investment fund, has announced that it will include climate change as an important factor in how it assigns risks to its investment portfolio … BlackRock is not your average investment fund. With $4.9 trillion in … Continue reading

Posted in adaptation, American Association for the Advancement of Science, American Meteorological Association, American Solar Energy Society, American Statistical Association, AMETSOC, Anthropocene, Bloomberg, Bloomberg New Energy Finance, BNEF, Buckminster Fuller, business, Carbon Worshipers, central banks, clean disruption, CleanTechnica, climate business, climate change, climate disruption, consumption, corporate litigation on damage from fossil fuel emissions, decentralized electric power generation, decentralized energy, destructive economic development, distributed generation, Ecology Action, economics, electricity markets, environment, Equiterre, extended supply chains, fossil fuel divestment, fossil fuels, geophysics, global warming, green tech, greenhouse gases, grid defection, Hyper Anthropocene, investing, investment in wind and solar energy, Joseph Schumpeter, leaving fossil fuels in the ground, liberal climate deniers, Mark Jacobson, meteorology, Our Children's Trust, Principles of Planetary Climate, quantitative ecology, Sankey diagram, science, science denier, Science magazine, Scripps Institution of Oceanography, sea level rise, shorelines, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, Stanford University, stranded assets, supply chains, sustainability, the energy of the people, the green century, the right to be and act stupid, the right to know, the tragedy of our present civilization, the value of financial assets, Tony Seba, transparency, UNFCCC, utility company death spiral, wind energy, wind power, Woods Hole Oceanographic Institution, zero carbon | Tagged , | Leave a comment

Just a lil’ bit o’ a drought … Nothing to be alarmed about … (!)

Posted in adaptation, American Meteorological Association, AMETSOC, Anthropocene, atmosphere, climate change, climate data, climate disruption, drought, environment, fluid dynamics, global warming, greenhouse gases, hydrology, Hyper Anthropocene, leaving fossil fuels in the ground, meteorology, quantitative ecology, Spaceship Earth, statistics, time series, water, water vapor, WHOI, zero carbon | Leave a comment

Generation: Westwood Studios, September 2016

(Click on image to see a larger figure, and use browser Back Button to return to blog.) (Click on image to see a larger figure, and use browser Back Button to return to blog.) As mentioned before, you can watch … Continue reading

Posted in American Meteorological Association, American Solar Energy Society, AMETSOC, Anthropocene, Buckminster Fuller, climate disruption, Hermann Scheer, Hyper Anthropocene, Sankey diagram, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, the energy of the people, the green century, the right to be and act stupid, the right to know, the value of financial assets, Tony Seba, zero carbon | 1 Comment

Republican Governor Charles D. Baker, The Commonwealth of Massachusetts: On CLIMATE

An Executive Order, No. 569 ESTABLISHING AN INTEGRATED CLIMATE CHANGE STRATEGY FOR THE COMMONWEALTH WHEREAS, climate change presents a serious threat to the environment and the Commonwealth’s residents, communities, and economy; WHEREAS, extreme weather events associated with climate change present … Continue reading

Posted in adaptation, American Association for the Advancement of Science, American Meteorological Association, AMETSOC, Anthropocene, Bloomberg New Energy Finance, BNEF, climate business, climate change, climate disruption, climate economics, climate education, climate justice, coastal communities, engineering, environment, environmental law, evidence, forecasting, fossil fuel divestment, fossil fuels, gas pipeline leaks, Gaylord Nelson, geophysics, global warming, green tech, hurricanes, Hyper Anthropocene, insurance, investing, investment in wind and solar energy, leaving fossil fuels in the ground, Massachusetts, Massachusetts Clean Energy Center, Massachusetts Interfaith Coalition for Climate Action, meteorology, Minsky moment, mitigation, moral leadership, rate of return regulation, rationality, reason, reasonableness, risk, shorelines, stranded assets, sustainability, the right to know, transparency, zero carbon | Leave a comment

“Predicting annual temperatures a year ahead” (Dr Gavin Schmidt at REALCLIMATE)

Dr Schmidt is essentially betting that the trend, seen as a random variable, will regress towards the smooth mean. I have a post at Nate Silver’s 538 site on how we can predict annual surface temperature anomalies based on El … Continue reading

Posted in American Meteorological Association, American Statistical Association, AMETSOC, anomaly detection, Anthropocene, changepoint detection, climate change, climate data, climate disruption, climate education, climate models, ecology, environment, forecasting, geophysics, global warming, Hyper Anthropocene, meteorology, oceanography, physics, regression toward the mean, science, statistics, time series | Leave a comment

“Sharon’s Water Problem” (by Paul Lauenstein)

(Click on image to see a bigger version of this figure. Use your browser Back Button to return to this blog.) The town of Sharon, MA, has a water problem. Click on the link and see Paul’s presentation about it. … Continue reading

Posted in adaptation, agriculture, American Meteorological Association, AMETSOC, Anthropocene, Boston, citizen science, climate change, climate disruption, diffusion processes, drought, ecology, Ecology Action, environment, forecasting, global warming, hydrology, Hyper Anthropocene, MA, New England, Paul Lauenstein, precipitation, quantitative ecology, science, statistics, the tragedy of our present civilization, water, Woods Hole Oceanographic Institution | Leave a comment

“Getting our heads out of the sand: The facts about sea level rise” (Robert Young)

If current luck holds, North Carolina may well escape the 2013 hurricane season without the widespread damage that has so frequently plagued the fragile coastal region in recent years. Unfortunately, this brief respite is almost certainly only that — a … Continue reading

Posted in American Association for the Advancement of Science, American Meteorological Association, American Statistical Association, AMETSOC, Anthropocene, Boston, climate, climate change, climate disruption, climate economics, coastal communities, coasts, ecology, environment, evidence, global warming, hurricanes, Hyper Anthropocene, living shorelines, Massachusetts, National Park Service, New England, nor'easters, oceanography, quantitative ecology, risk, Robert Young, science, sea level rise, shorelines, spatial statistics, sustainability, the right to be and act stupid, the right to know, the tragedy of our present civilization, the value of financial assets | 1 Comment

Repaired R code for Markov spatial simulation of hurricane tracks from historical trajectories

I’m currently studying random walk and diffusion processes and their connections with random fields. I’m interested in this because at the core of dynamic linear models, Kalman filters, and state-space methods there is a random walk in a parameter space. … Continue reading

Posted in American Meteorological Association, American Statistical Association, AMETSOC, Arthur Charpentier, atmosphere, diffusion, diffusion processes, dynamic linear models, dynamical systems, environment, geophysics, hurricanes, Kalman filter, Kerry Emanuel, Lévy flights, Lorenz, Markov chain random fields, mathematics, mathematics education, maths, MCMC, mesh models, meteorological models, meteorology, model-free forecasting, Monte Carlo Statistical Methods, numerical analysis, numerical software, oceanography, open data, open source scientific software, physics, random walk processes, random walks, science, spatial statistics, state-space models, statistical dependence, statistics, stochastic algorithms, stochastics, time series | Leave a comment

Bayesian blocks via PELT in R

The Bayesian blocks algorithm of Scargle, Jackson, Norris, and Chiang has an enthusiastic user community in astrostatistics, in data mining, and among some in machine learning. It is a dynamic programming algorithm (see VanderPlas referenced below) and, so, exhibits optimality … Continue reading

Posted in American Statistical Association, AMETSOC, anomaly detection, astrophysics, Cauchy distribution, changepoint detection, engineering, geophysics, multivariate statistics, numerical analysis, numerical software, numerics, oceanography, population biology, population dynamics, Python 3, quantitative biology, quantitative ecology, R, Scargle, spatial statistics, square wave approximation, statistics, stepwise approximation, time series, Woods Hole Oceanographic Institution | Leave a comment

Richard Somerville, UCSD, Scripps: “The science is becoming more widely accepted”

By Richard Somerville, emiritus professor of Oceanography from Scripps Institution of Oceanography. See the site he helps build and run regarding communication regarding change.

Posted in adaptation, American Meteorological Association, AMETSOC, Anthropocene, atmosphere, citizenship, civilization, climate, climate change, climate disruption, environment, forecasting, global warming, meteorology, oceanography, Principles of Planetary Climate, science, Scripps Institution of Oceanography, the right to know, the tragedy of our present civilization, University of California, zero carbon | Leave a comment

Rushing the +2 degree Celsius boundary

I made a comment on Google+ pertaining to a report of a recent NOAA finding. Enjoy. But remember that COP21 boundary is equivalent to 450 ppm CO2.

Posted in adaptation, AMETSOC, Anthropocene, atmosphere, Bill Nye, bridge to nowhere, carbon dioxide, Carbon Tax, Carbon Worshipers, citizenship, civilization, clean disruption, climate, climate disruption, COP21, corporate litigation on damage from fossil fuel emissions, differential equations, disruption, distributed generation, Donald Trump, ecology, El Nina, El Nino, energy, energy reduction, engineering, environment, environmental law, Epcot, explosive methane, forecasting, fossil fuel divestment, fossil fuels, geophysics, global warming, greenhouse gases, greenwashing, Hyper Anthropocene, investment in wind and solar energy, IPCC, local generation, Mark Jacobson, Martyn Plummer, microgrids, Miguel Altieri, philosophy, physical materialism, R, resiliency, Ricky Rood, risk, Sankey diagram | Leave a comment