(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."