It is June 2024. To the click of camera shutters, newly elected Prime Minister Rishi Sunak and Deputy Prime Minister Caroline Lucas stroll through the rose garden of 10 Downing Street. Their opening speeches hail a “new era of Conservative-Green government”, preserving the environment while supporting business and tradition. Right now, it is an unlikely image. But by 2024 it may be a familiar pairing.

On the 1^st January this year, talks in Austria produced a coalition between the conservative ÖVP and the Greens – the artfully crumpled attire of Green leader Werner Kogler a strange counterpoint to the persistently suave chancellor Sebastien Kurz. In June, a new Irish government was confirmed when Green Party members voted to join Fine Gael and Fianna Fáil. In German elections next year, a Green-CDU/CSU coalition is the odds-on outcome. Friedrich Merz, a right-wing hopeful to succeed Angela Merkel, claimed green-conservative values have “long been around the breakfast table” to Der Spiegel while posing in a green suit and tie.

Green parties have been part of European coalitions in past decades, for example in Finland and Sweden.  But today’s environmentalism has a new flavour. The visibility of Extinction Rebellion, and the totemic issue of reaching ‘net zero’, presents a stark central message – change fast, or face extinction. This existential threat may have helped the surge in green support across Europe, much as right-wing populists have capitalised on alleged existential threat to ‘national culture’ from immigration. But whatever its electoral success, this messaging may not be a comfortable basis for green-conservative partnerships.

Some traditional green themes, particularly preserving nature and the world ‘for our grandchildren’, sit easily with conservative mindsets. Not so much the radical anti-capitalist rhetoric of Extinction Rebellion. Green parties in many countries across Europe – particularly around the Mediterranean, but also in the UK – are strongly associated with left-wing politics. In these countries, political circumstances and electoral systems mean Green parties already struggle at the ballot box. But were they to unexpectedly reach coalition talks with conservatives, one could expect difficulties.

Greens in Northern Europe and Ireland do not have quite such strong ideological stances, but there are still tensions. In Der Spiegel, Merz suggested some CDU voters may be “put off by the ideologues among the Greens”. Conversely the Austrian Greens have historically fought for “social and cultural minorities”; they are now supporting a party which banned headscarves in schools. But in return Austria now has a “super-ministry” for the environment and an ambitious goal of carbon neutrality by 2040. Party memberships seem willing to try compromise – 93% of Austrian Green delegates, and 76% of Irish Green Party members, voted in favour of coalition. But there are already accusations that such arrangements “dissolve the climate movement’s demands in a greenwashed rightwing project. ”

Junior coalition parties have always been vulnerable to threats from both their supporters and governing partners – just ask the Liberal Democrats, or the Finns Party. But coalitions hold at least two vital opportunities for Green parties. The first is firmly keeping their partners to promised environmental targets. Here they can ally with green politicians increasingly filling other posts, from city mayors to the European Parliament; but coalition parties have a unique power to hold governments to promises. The second is a position to influence other high-emission countries, particularly those where domestic green movements struggle to have much sway. Without such international changes, even a few successfully met net-zero targets will be of little consequence.

Speaking less than a week into the new Austrian coalition, Werner Kogler neatly captured the situation facing greens in government.  He was ambivalent about the coalition arrangement, declining to call it “the best of both worlds”. Instead he emphasised that “es gibt nur eine Welt” (there is only one world). In doing so he hinted at friction already lurking in the partnership – but also the stakes involved in its success. Ultimately greens in coalition face that central tension of government: high ideals meeting technocratic reality. But they do so on a deadline.

Owen Marsh is an independent researcher into the role of science and technology in political futures.