In a powerful display of climate activism, campaigners kicked off the Summer of Heat program by blockading the entrances to Citigroup's headquarters in New York City. The protesters, affiliated with organizations such as Climate Defenders and Stop the Money Pipeline, aimed to bring attention to Citigroup's role in perpetuating climate breakdown.

Taking to social media, Climate Defenders stated that hundreds of activists had gathered to shut down Citibank's Global HQ, demanding a future free from fossil fuels. Citigroup, the parent company of Citibank, has come under fire for financing more fossil fuel expansion than any other bank since the signing of the 2015 Paris agreement.

The nonviolent direct action organized by the Summer of Heat campaign began on Monday, with campaigners locking arms and holding banners at the doors of Citigroup offices, effectively blocking hundreds of employees from entering. Video footage and social media posts captured police arresting a number of activists throughout the day.

Renata Pumarol, deputy director of Climate Defenders, reported that dozens of protesters had been arrested by 10:50 am ET, although an exact figure was not available at the time. Stop the Money Pipeline emphasized that their message was clear: if financial institutions continue to fund fossil fuel companies that disrupt the climate and people's lives, their ability to do business will be disrupted in return.

During the blockade, an activist wearing a Scientist Rebellion badge and a lab coat stated that Citibank's substantial investment in expanding fossil fuels is a crime against the planet. The Union of Concerned Scientists (UCS) voiced their support for the action by publishing an open letter to Citigroup CEO Jane Fraser, urging the bank to halt funding for new fossil fuel projects.

According to the UCS, the financial industry must acknowledge the physical and economic risks it exacerbates by enabling fossil fuel expansion and adopt policies aligned with a safer climate future. On Wednesday, UCS plans to deliver their message to Citigroup CEO Fraser during a "Scientists Speakout" event outside the headquarters.

The blockade of Citigroup's headquarters marks an important moment in the Summer of Heat campaign, demonstrating the growing momentum and urgency of the climate activism movement. As activists continue to push for change, they emphasize the need for financial institutions like Citigroup to divest from fossil fuels and support a more sustainable future.

As this is a developing story, further updates may follow.

(Note: This article is derived from the information provided and includes no additional entities, numbers, or dates.