(CNN) Local communities almost always pull together on the ground after natural disasters like the torrential flooding that has submerged Houston. 
 
 But the aftermath of Hurricane Harvey is likely to strain America's fraying capacity to coalesce as a national community at a moment of heightened political conflict and division. 
 
 Amid the images of devastation and loss, Americans this weekend repeatedly watched stirring scenes of ordinary people organizing makeshift flotillas to rescue families trapped in the epic flooding. In the rising waters, partisan, racial and class lines all seemed to dissolve. 
 
 Yet, once the immediate danger has passed, the response to the storm will raise larger political questions on at least two major fronts: the cost of recovery and the role of climate change in intensifying the risk of such devastating storms. Each of those issues will challenge America's ability to surmount its differences enough to set a shared national direction. Like Hurricane Katrina and Superstorm Sandy before it, Harvey may demonstrate just how much the man-made gales of political polarization has diminished the nation's capacity to forge common cause against even the fiercest natural disasters. 
 
 A recent history of funding fights 
 
 The first issue that will test the nation's unity is funding the recovery from the storm. Federal figures put the cost of damages from Katrina in 2005 that devastated New Orleans and the Gulf Coast at $160 billion, and from Sandy in the New York and New Jersey area in 2012 at around $70 billion. Early estimates on the potential damages from Harvey vary, but experts are anticipating losses totaling tens of billions of dollars. 
 
 In recent years, Congress has faced unprecedented partisan divides over Washington's role in meeting those costs. In 2005, Vice President Mike Pence, then a Republican congressman from Indiana, led an effort by House conservatives to offset any post-Katrina aid with offsetting budget cuts in other programs, including highway projects and the new Medicare prescription drug benefit. "We simply can't allow a catastrophe of nature to become a catastrophe of debt for our children and grandchildren," Pence said at the time. 
 
 Even more partisan -- and regional -- conflict flared after Sandy slammed into New York and New Jersey just before the 2012 presidential election. That storm precipitated a succession of confrontations between conservative Republicans in both chambers against a coalition of Republicans from the region and Democrats. 
 
 In those debates, Mick Mulvaney, now director of the Office of Management and Budget and then a Republican congressman from South Carolina, echoed Pence during Katrina by proposing legislation to offset Sandy aid with across-the-board reductions in domestic programs. That amendment failed, but over two-thirds of House Republicans voted for it, including an array of prominent Texans still in Congress. That list of supporters included Representatives Kevin Brady (now chair of the House Ways and Means Committee); Jeb Hensarling (now chair of the House Financial Services Committee) and Pete Sessions. Also voting for Mulvaney's legislation was Paul Ryan, now the House Speaker. 
 
 Eventually the vast majority of Republicans in both chambers -- 179 in the House and 36 in the Senate -- voted against the final $50 billion federal aid package for Sandy, arguing that the bill was bloated with extraneous projects. The Republican opponents included both of Texas' senators -- John Cornyn and Ted Cruz -- and a lengthy list of Texas House Republicans, including Brady and Hensarling. 
 
 Demanding offsetting cuts complicates responding to natural disasters both at the tactical and philosophical level. The tactical problem is that it ensures a more partisan and protracted Congressional debate. The philosophical problem may be even more telling. Demanding cuts sets the interests of one geographic area against the national web of communities reliant on the programs facing reductions. In essence, demanding that some communities suffer funding losses in ongoing programs to offset assistance to places facing acute needs undermines the core idea that government exists in part to help share risks that individuals, and even individual communities, cannot reasonably bear alone. 
 
 "Saying, 'we will do this for hurricanes in the Gulf Coast or the East Coast or tornadoes in the Midwest or earthquakes in California,' is a way of saying government as a social institution is there to help society deal with things that at the levels of individuals you can't reasonably be expected to deal with," said Richard Kogan, a senior analyst at the Center on Budget and Policy Priorities a liberal research and advocacy group. 
 
 These earlier skirmishes raise the question of whether Congressional conservatives, including those from Texas, will again insist on offsetting any aid for Houston and the Gulf Coast with spending cuts elsewhere. Such a move would inevitably extend the Congressional debate over aid and provoke an instant partisan split. No floodwaters could sweep away any sense of shared national concern over the disaster faster than a Congressional debate that frames aid to Texas against programs that benefit communities elsewhere. 
 
 Climate change as a concern 
 
 The nation's ability to maintain a common purpose will be tested even more severely when the discussion eventually turns to whether climate change is increasing the risk of catastrophic storms like Harvey. 
 
 Scientists remain leery of attributing any individual storm to climate change. But the dominant scientific consensus is that climate change is increasing the odds that storms will be more powerful and destructive. 
 
 "There is no doubt that climate change increases the severity of disasters such as Hurricane Harvey," Jane Lubchenco, the administrator of the National Oceanic and Atmospheric Administration under former President Obama told me in an email exchange Monday. "Warmer ocean waters are more conducive to more intense hurricanes (heat = energy). Warmer air holds more moisture. Climate change is warming both the ocean and the air. In addition, higher sea levels mean greater storm surge. As we're seeing with Harvey, the combination is devastating: powerful winds, incessant downpours, significant flooding. " 
 
 In another email exchange on Monday, John W. Nielsen-Gammon, the Texas State climatologist and a professor of atmospheric sciences at Texas A&M, was quick to argue that it was premature to directly link Harvey specifically to changes in the climate. "The climate change impact on the strength of Harvey is unknown; climate change is expected to increase the intensity of the strongest storms, but it's not clear whether Harvey was in that category," he wrote me. 
 
 But Nielsen-Gammon added that the overall trajectory of extreme weather in Texas is unmistakable-and strongly linked to climate change. "Extreme rainfall, however, is getting heavier: The south-central United States has seen an increase in the frequency and intensity of one-day and two-day extreme rainfall events," he wrote. "My own analysis of Texas data shows an increase of about 30% in the likelihood of passing a given threshold [of total rain amount] in a given year, which corresponds to about a 5% increase in the intensity of the strongest rainfall over the past century." 
 
 That shift, he continued, "is a direct consequence of climate change and is expected to continue." Like Lubchenco and other climate scientists, Nielsen-Gammon said the increasing incidence of heavy storms is "driven by rising atmospheric temperatures and rising sea surface temperatures, which affect the capacity of the atmosphere to hold moisture and increases the total amount of water that can rain out when the air is saturated." 
 
 President Donald Trump has dismissed climate change as a "hoax"; the Environmental Protection Agency is in the process of uprooting the major regulatory initiatives Obama undertook to reduce carbon emissions from power plants, cars and trucks. Trump also withdrew the US from the Paris global climate accord. 
 
 In advancing this agenda, Trump has operated with a clear regional tilt, favoring the interests of the states that are most reliant on producing fossil fuels, or consuming them for electricity. That reflects Trump's electoral base: he won 13 of the 16 states that produce the most natural gas, 16 of the 20 that produce the most oil, and 11 of the 15 that mine meaningful amounts of coal. 
 
 Yet by prioritizing the immediate interests of these resource-producing states, Trump has slighted the national interest in controlling the risks associated with a changing climate. The irony is that, as Katrina and Harvey have both demonstrated, some of the states most invested in the fossil fuel economy are also at the greatest risk if climate changes spawns more severe storms. 
 
 "Unfortunately, climate change will most certainly make disasters like Hurricane Harvey more likely: Think of Harvey as a glimpse of the future," Lubchenco, now a distinguished university professor at Oregon State University, wrote me. "The smart move would be to be better prepared (i.e., to expect this to happen more often, not be surprised by it, and prepare accordingly), to reduce carbon emissions faster than we are now (much faster), and to invest in enhanced research and monitoring that will enable continued improvement of forecasting of events like this." ||||| By the time the rain stops, Harvey will have dumped about 1 million gallons of water for every man, woman and child in southeastern Texas — a soggy, record-breaking glimpse of the wet and wild future that global warming could bring, scientists say. 
 
 While scientists are quick to say that climate change didn't cause Harvey and that they haven't determined yet whether the storm was made worse by global warming, they do note that warmer air and water mean wetter and possibly more intense hurricanes in the future. 
 
 "This is the kind of thing we are going to get more of," said Princeton University climate scientist Michael Oppenheimer. "This storm should serve as warning." 
 
 There's a scientifically accepted method for determining if some wild weather event has the fingerprints of man-made climate change, and it involves intricate calculations. Those could take weeks or months to complete, and then even longer to pass peer review. 
 
 In general, though, climate scientists agree that future storms will dump much more rain than the same size storms did in the past. 
 
 That's because warmer air holds more water. With every degree Fahrenheit, the atmosphere can hold and then dump an additional 4 percent of water (7 percent for every degree Celsius), several scientists say. 
 
 Global warming also means warmer seas, and warm water is what fuels hurricanes. 
 
 When Harvey moved toward Texas, water in the Gulf of Mexico was nearly 2 degrees (1 degree Celsius) warmer than normal, said Weather Underground meteorology director Jeff Masters. Hurricanes need at least 79 degrees F (26 C) as fuel, and water at least that warm ran more than 300 feet (100 meters) deep in the Gulf, according to University of Miami hurricane researcher Brian McNoldy. 
 
 Several studies show that the top 1 percent of the strongest downpours are already happening much more frequently. Also, calculations done Monday by MIT meteorology professor Kerry Emanuel show that the drenching received by Rockport, Texas, used to be maybe a once-in-1,800-years event for that city, but with warmer air holding more water and changes in storm steering currents since 2010, it is now a once-every-300-years event. 
 
 There's a lot of debate among climate scientists over what role, if any, global warming may have played in causing Harvey to stall over Texas, which was a huge factor in the catastrophic flooding. If the hurricane had moved on like a normal storm, it wouldn't have dumped as much rain in any one spot. 
 
 Harvey stalled because it is sandwiched between two high-pressure fronts that push it in opposite directions, and those fronts are stuck. 
 
 Oppenheimer and some others theorize that there's a connection between melting sea ice in the Arctic and changes in the jet stream and the weather patterns that make these "blocking fronts" more common. Others, like Masters, contend it's too early to say. 
 
 University of Washington atmospheric scientist Cliff Mass said that climate change is simply not powerful enough to create off-the-chart events like Harvey's rainfall. 
 
 "You really can't pin global warming on something this extreme. It has to be natural variability," Mass said. "It may juice it up slightly but not create this phenomenal anomaly." 
 
 "We're breaking one record after another with this thing," Mass said. 
 
 Sometime Tuesday or early Wednesday, parts of the Houston region will have broken the nearly 40-year-old U.S. record for the heaviest rainfall from a tropical system — 48 inches, set by Tropical Storm Amelia in 1978 in Texas, several meteorologists say. 
 
 Already 15 trillion gallons of rain have fallen on a large area, and an additional 5 trillion or 6 trillion gallons are forecast by the end of Wednesday, meteorologist Ryan Maue of WeatherBell Analytics calculates. That's enough water to fill all the NFL and Division 1 college football stadiums more than 100 times over. ||||| What can we say about the role of climate change in the unprecedented disaster that is unfolding in Houston with Hurricane Harvey? There are certain climate change-related factors that we can, with great confidence, say worsened the flooding. 
 
 What we know so far about tropical storm Harvey Read more 
 
 Sea level rise attributable to climate change – some of which is due to coastal subsidence caused by human disturbance such as oil drilling – is more than half a foot (15cm) over the past few decades (see here for a decent discussion). That means the storm surge was half a foot higher than it would have been just decades ago, meaning far more flooding and destruction. 
 
 In addition to that, sea surface temperatures in the region have risen about 0.5C (close to 1F) over the past few decades from roughly 30C (86F) to 30.5C (87F), which contributed to the very warm sea surface temperatures (30.5-31C, or 87-88F). 
 
 
 
 There is a simple thermodynamic relationship known as the Clausius-Clapeyron equation that tells us there is a roughly 3% increase in average atmospheric moisture content for each 0.5C of warming. Sea surface temperatures in the area where Harvey intensified were 0.5-1C warmer than current-day average temperatures, which translates to 1-1.5C warmer than “average” temperatures a few decades ago. That means 3-5% more moisture in the atmosphere. 
 
 That large amount of moisture creates the potential for much greater rainfalls and greater flooding. The combination of coastal flooding and heavy rainfall is responsible for the devastating flooding that Houston is experiencing. 
 
 Not only are the surface waters of the Gulf of Mexico unusually warm right now, but there is a deep layer of warm water that Harvey was able to feed upon when it intensified at near record pace as it neared the coast. Human-caused warming is penetrating down into the ocean. It’s creating deeper layers of warm water in the Gulf and elsewhere. 
 
 Sea surface temperatures in the region have risen about 0.5C (close to 1F) over the past few decades 
 
 Harvey was almost certainly more intense than it would have been in the absence of human-caused warming, which means stronger winds, more wind damage and a larger storm surge. (As an example of how this works, we have shown that climate change has led to a dramatic increase in storm surge risk in New York City, making devastating events like Hurricane Sandy more likely.) 
 
 Finally, the more tenuous but potentially relevant climate factors: part of what has made Harvey such a devastating storm is the way it has stalled near the coast. It continues to pummel Houston and surrounding regions with a seemingly endless deluge, which will likely top out at nearly 4ft (1.22m) of rainfall over a days-long period before it is done. 
 
 The stalling is due to very weak prevailing winds, which are failing to steer the storm off to sea, allowing it to spin around and wobble back and forth. This pattern, in turn, is associated with a greatly expanded subtropical high pressure system over much of the US at the moment, with the jet stream pushed well to the north. This pattern of subtropical expansion is predicted in model simulations of human-caused climate change. 
 
 More tenuous, but possibly relevant still, is the fact that very persistent, nearly “stationary” summer weather patterns of this sort, where weather anomalies (both high-pressure dry hot regions and low-pressure stormy/rainy regions) stay locked in place for many days at a time, appears to be favoured by human-caused climate change. We recently published a paper in the academic journal Scientific Reports on this phenomenon. 
 
 In conclusion, while we cannot say climate change “caused” Hurricane Harvey (that is an ill-posed question), we can say is that it exacerbated several characteristics of the storm in a way that greatly increased the risk of damage and loss of life. Climate change worsened the impact of Hurricane Harvey.
– As the deluge continues in Houston, one big question being debated is what role, if any, climate change played in the storm. As with most debates on climate change—particularly when talking about a single weather event—the views are all over the map. And some are suggesting that we need to frame the question differently to get the most accurate response. The details: Wrong question: Did climate change cause Harvey? That's not the right question, writes Dino Grandoni at the Washington Post. "The better way to frame thinking about the connection is through the question: Does climate change make storms like Harvey more likely?" This is a theme repeated in multiple posts on the subject, and Grandoni thinks the answer is yes, for reasons spelled out below. 'Worsened': One of the most cited pieces is from Penn State professor Michael Mann in the Guardian. "We can't say that Hurricane Harvey was caused by climate change," he writes. "But it was certainly worsened by it." The three big factors: Higher ocean levels made the storm surge worse, warmer water made the storm more intense, and Harvey stayed "locked in place" thanks to atmospheric changes brought on by humans. (The latter was the subject of a paper by Mann.) Maybe 'slightly': University of Washington atmospheric scientist Cliff Mass is skeptical the link is that strong. "You really can't pin global warming on something this extreme," he tells Fox News. "It has to be natural variability. It may juice it up slightly but not create this phenomenal anomaly." Link is 'unknown': Texas State climatologist John Nielsen-Gammon thinks it's too early to assess any link. "The climate change impact on the strength of Harvey is unknown," he writes to CNN. "Climate change is expected to increase the intensity of the strongest storms, but it's not clear whether Harvey was in that category." Still, he notes that heavier rain in general is a "direct consequence" of climate change, and Harvey certainly fits that pattern. Too 'fussy': David Leonhardt at the New York Times thinks "it's time to shed some of the fussy over-precision about the relationship between climate change and weather." The evidence is overwhelming that human-caused climate change results in storms such as Harvey, he writes, and our timidness in admitting it is holding up solutions. All about the rain: The jury is out on whether climate change increases the frequency of hurricanes, writes David Roberts in a wide-ranging Q&A at Vox. But he, too, says it's clear that heavier rain is an undisputed consequence. "In fact, due to sea level rise and more moisture in the air, I expect flooding to be the most frequent public face of climate change over the next decade or so." Media coverage: You won't hear much about climate change in the current news coverage because reporters don't want to "politicize" the situation, writes Naomi Klein at the Intercept. "But here's the thing: Every time we act as if an unprecedented weather event is hitting us out of the blue, as some sort of Act of God that no one foresaw, reporters are making a highly political decision," she notes. In contrast, panelists on Fox's The Five spotted a CNN banner mentioning climate change and accused the network of pushing a liberal agenda. "It's called the weather," said co-host Jesse Watters.