On Saturday I joined the March for Science in Washington DC to show solidarity with American climate researchers who sent a message of defiance to President Trump and his administration.
I made the journey across the Atlantic because the Trump administration's ideological war against climate science is increasing risks for families and businesses not only in the United States, but across the world.
Climate scientists perform a vital public service by investigating and analysing the threats posed by rising sea levels, shifts in extreme weather and other impacts of growing greenhouse gas levels in the atmosphere.
But American climate scientists have been, for many years, targeted by politicians, oil companies, lobbyists and parts of the media that are opposed to action on climate change.
The scientists have been subjected to verbal and written attacks, and campaigns to undermine the credibility of their research.
So on Saturday I marched wearing a T-shirt for the Climate Science Legal Defense Fund, which was set up in 2011 to support climate scientists who are dragged into litigation or otherwise threatened with legal attacks and harassment by politically and ideologically motivated groups.
The Fund has helped many climate scientists in recent years, including Professor Michael Mann, who has had to repel legal efforts to gag him by Republican politicians and right-wing lobby groups.
The Fund is unique and its work is needed now more than ever, so I will also be raising sponsorship for it when I run a marathon at Crater Lake in Oregon in August.
I marched alongside many climate scientists on Saturday who were protesting at the political war against their profession since President Trump's inauguration on 20 January.
President Trump has appointed a number of climate change deniers to his administration, including Scott Pruitt, the head of the Environmental Protection Agency, who recently claimed that human activity is not "a primary contributor to the global warming that we see".
Last month, the White House proposed major cuts to the Agency's spending and staff, with Mick Mulvaney, Director of the Office of Management and Budget, telling a press conference that funding for climate programmes was "a waste of your money".
But the Trump administration's assault on climate science is not limited to the Environmental Protection Agency. The President's blueprint for the federal budget in 2018 includes measures to hobble climate research and data monitoring across a number of agencies.
For instance, it would end support for four NASA missions to monitor the Earth's climate.
One of these missions is already operational, with the Deep Space Climate Observatory (DSCOVR) satellite having been launched in February 2015.
But the budget proposes to stop money being spent on the "DSCOVR Earth-viewing instruments", while continuing support for the instruments directed towards outer space.
The budget also takes money away from a satellite programme created by the National Oceanic and Atmospheric Administration to provide better information about polar climates.
Meanwhile the Trump administration's allies in Congress have also been striking at climate scientists.
For instance, Lamar Smith, the Chair of the House of Representatives Committee on Science, Space and Technology, has been continuing his campaign to discredit a paper by scientists at the National Oceanic and Atmospheric Administration which concluded there was no 'pause' in the rate of global warming during the first 15 years of the 21stcentury.
These attempts to silence climate scientists appear to be part of an insidious plan to deprive the American people of the truth about climate change. Not only does the Trump administration want to stop American families and businesses from accessing information on federal websites that draw on the work of climate scientists, they want to stop knowledge-gathering altogether.
But it will not only be Americans who suffer from this censorship of climate scientists. Policy-makers and their citizens all around the world currently rely on the results of world class research and data-gathering by climate scientists in the United States.
Hence, the Trump administration's war on climate science will create casualties in many other countries, including the UK, if it leads to decisions that are not informed by the best research.
That is why I helped to organise a letter to the Prime Minister, Theresa May, in January from 100 members of the UK climate research community to warn of the consequences of an ideological crusade by President Trump.
On Saturday I tried to highlight these threats again and to show American climate scientists that their counterparts in the UK and around the world are shoulder to shoulder with them as they stand up for their profession.
Bob Ward is policy and communications director at the Grantham Research Institute on Climate Change and the Environment at the London School of Economics and Political Science, and a Fellow of both the Geological Society and the Royal Geographical Society.